Telephones: a weak link in remote broadcasting | radioinfo

Telephones: a weak link in remote broadcasting

Tuesday 02 June, 2020
Wilko and Courts, Hit 104.7 Canberra

Have you been listening to the quality of telephone calls on radio during this time of lockdown? Most of them are pretty bad.

Steve Ahern asks a range of technical experts about the causes and solutions to bad phone lines during this time. This is a long article, so we've provided a table of contents so you can skip around if you want to

I have been hearing lots of very bad telephone lines on radio since the lockdowns began and it started me thinking about the causes and possible solutions.

The more I thought about it, the more I identified multiple points of failure during these changed broadcasting circumstances.

These are some of the things I have heard:

  • Echo on the line
  • Crosstalk
  • Poor signal strength style mobile phone dropouts
  • Digital drop outs
  • Speed changes
  • Profanity Delay errors

This is what I think is happening:

  • Echo on the line - the presenters are using zoom or some other video/audio conferencing system but there is not enough echo cancelling being applied. Plus there is likely no mix-minus mic clean-feed capability in remote studios.
  • Crosstalk - this seems to me like the skype, zoom or other digital conference system is overloaded and there are artefacts from other calls on the line.
  • Poor signal strength style mobile phone dropouts - this is standard, but because there are more people using their mobiles from home, I suspect the cell towers in residential areas are overloaded because they are not equipped for peak load capacity during business hours, like towers in the CBD.
  • Digital drop outs - this could be the phone line, or more likely it is a data capacity issue on the line between the studio and the presenter’s house.
  • Speed changes - this is common when using skype, zoom, messenger, viber etc as the system tries to balance poor internet capacity by slowing or freezing the data stream momentarily, then catching it up once capacity improves to get back into real time. Bluetooth headphones can also be a weak point here are they sometimes distort the audio if there is interference.
  • Profanity Delay errors - After all the other factors are taken into consideration, there’s the profanity delay system to think about as well. Who can dump? Where from? Is the remote caller dumped too? How is the ramp back into delay handled? How does delay work on multiple transmission/stream paths with at least one more  source studio added to the mix?

All this made my brain hurt. So I asked some experts to explain their experiences and sought advice about these questions:

  • Are voice landlines still be best quality?
  • Is there really any such things as a landline any more in this era of NBN? Aren’t they all just data lines?
  • The next best option after landlines should be voice calls via mobile phones, but if mobile voice calls use the data stream of each cell, and the data capacity for voice calls is compromised by overloading of cell tower capacity, is there any benefit in mobile voice calls any more?
  • Do voice calls still get dedicated bandwidth on cell networks, or are they all just data now?
  • Non professional data call options include zoom, skype, whats app, messenger, etc. These are normally good because they can deliver better frequency response, but during this time there is so much data traffic that they are almost always interrupted in some way.
  • There are also some professional level options too, how do they work? If you have a professional system on one end, but the caller just has a plain old normal phone, is it any value?
  • Or, maybe it is not the phones at all, maybe it is unstable bandwidth from home studios being used be presenters remotely. For internet access the weak point is usually the last mile to the home. Providers had little incentive to fix this issue in the past, because most traffic was through big pipes in CBDs. Now it is dispersed.

Here’s what the experts told me.

ARN’s Technology Director, Joe Sexton
Well spotted, the mobile network congestion in particular was pretty bad in the early weeks of COVID and did provide a few challenges. We had two challenges: Internal and External
ARN upgraded the internal PABX system in late 2019 which gave us a flexible IP solution for users. For example, desktop phones could be diverted to personal phones or to a soft client on laptops. For the Executive and Technology teams we extended the ARN network to personal ISPs and ARN desktop phones could be used at home. Personally, this was a life saver as my mobile was having constant issues.
We also had live callers who were having similar issues and quickly moved to IP which took several forms.
We took an agnostic approach where we would take any Digital format that was of acceptable quality for radio broadcasting. Technology was the enabler for great content.

In the case of the Kyle and Jackie O show, we used the enhanced audio algorithms (optional) of Zoom for an interview with Chris Hemsworth. In many ways,  it was the path of least resistance for our content teams and this included MS Teams, Google Meets or Hangouts, Zoom, Skype and Cisco VC tools. A lot of these have options for superior audio algorithms over GSM and 4G.
We also utilised Digigram’s 16 stereo channel IQOYA *SERV/LINK system, with the HTML5 Digigram routing system.  This solution meant that we could easily connect listeners and talent to studios using IP with Broadcast acceptable algorithms like OPUS.
We found the national Internet Service Providers (ISPs data) to be a lot more reliable than the mobile 3G/4G telco data (POTS/ISDN are not viable in the near future).
Audio quality is important but so is content and we’ll do whatever it takes to get great content to air.

SBS Manager of Radio Technology & Operations, Aaron Alphonso

Poor telephone quality / home studio contribution quality could be due to many reasons, including networks perhaps being overstretched and various other factors.
Here at SBS we developed a standard remote workflow procedure for social distancing that encourages the use of a commercially available professional remote audio contribution tool called ipDTL that can be accessed on a web browser without additional codec equipment. As a backup, we rely on Tieline ReportIT to connect to our existing Tieline codecs.  We also have a backup solution that relies on hardware codec devices.
These solutions are purpose built audio software codecs with low latency (delay) figures for remote audio contribution and voiceover work.
Because of this, they do not bother themselves with echo cancellation or mix minuses – they just focus on very high quality audio delivered with minimum delay, and trust that its being used by an operator that understands and has the facility to derive a true mix minus from the studio router or console.
We additionally equip our talent with specially selected headsets and audio interfaces pre-configured with the right EQ and dynamics settings built in to cater for a variety of home broadcasting scenarios.
Our disaster recovery plan includes using some of these more widely available video conferencing solutions, but we would only use it in an absolutely desperate bid to get someone on air, as echo cancellation is often not a strong point. Also audio bandwidth is poor, and it is very aggressively compressed, leading to noticeable audio problems when our listeners are hearing us on DAB+ or streaming, which as you know adds another encoding layer.
One thing that trips up these video conferencing systems and makes their echo cancellation algorithms work harder is talent not using headphones, or perhaps headphones that are not ‘closed-back’ which allow audio to bleed back into microphones.
I understand that not all networks may have the capacity or resources to use purpose built audio contribution solutions, and as such may rely on Zoom, Google Meet etc – my advice would be to please equip your talent with microphones that have excellent off-axis rejection.

The best microphone for remote working may not be the nicest looking large ‘studio like’ condenser microphone that our talent may desire, often these don’t work well in somebody’s kitchen or bedroom where there is a lot of unwanted noise reverberation from hard surfaces.  What we need are microphones that focus on picking up audio from the talent speaking directly into it, and not the entire untreated room. Also very important to ensure that they wear headphones or earphones that don’t bleed audio back into the mic.

Nine Radio Resources and Radio Technology Operations Manager Michael Sammut

I think there are a few things at play here.

Firstly, I've found that all the telcos are under enormous pressure during the coronavirus pandemic.  I've had several dealings with them while trying to arrange connectivity for outside broadcasts and setting up our talent to present from home and it's very apparent that they are having a difficult time keeping service levels up while the demand profile for their services has changed so dramatically and so quickly.

So I think in some cases poor line quality has been a reflection of the network under strain.

Secondly, in the early days it was a scramble to get enough equipment together in such a short time to facilitate all our remote broadcasts. I remember in particular one of our regular contributors in the first week - she was dialling in from her landline at home! I heard it go to air and was mortified - the next day I bought and shipped some equipment to her to solve that problem.

We're using a range of methods to enable remote broadcasting - the go-to is the Tieline ViA IP codec. We've also distributed a number of Rode NT USB microphones that we're using with the Tieline Report-IT iPhone app and that's been a great success.

With everybody broadcasting remotely and the immense strain this is placing on resources it's not surprising that you're hearing lower quality audio sneaking through a bit more. Frankly, it's a testament to the professionalism and skill of the engineers, producers and presenters in the Australian radio industry that in almost all cases nobody listening can even tell that it's very much not business as usual behind the scenes!

I don't think that the audio quality that we're putting to air is appreciably lower at this time. It's certainly been a challenge and we've not always been perfect but our systems are working and in fact we've taken the opportunity to learn and introduce some great new innovations that have made our remote broadcasts even more dynamic and flexible in ways that are delivering real value for our listeners.


Ian Campbell and Hayden Beetar from AVC Group
Some of our clients are getting great results with the latest ‘CallerOne’ version of PhoneBox (now called Bionic Studio).

It started off as just a phone system,  but now our remote options are in high demand during lockdown, as well as the audio and video capture and social media functions. It incorporates Skype and soon other systems such as WhatsApp.

Combining CallerOne with another of the options, called ‘Anywhere’  has given some great results for phone calls in remote studios.

With so many broadcast teams working from home studios, CallerOne can connect the team members from any location. A call screener might be at his home, the presenter is somewhere else and the panel operator is in the studio. The system works on a browser and each person can perform their functions from anywhere, then the others can see what’s happening in real time. So the call screener will answer and park a call, then use chat to tell the presenter to take the call on line 2. It is possible for the presenter to put that caller to air from their home studio, or, if there is a panel op at the studio, they can take the call through the desk.

With the Anywhere function, producers can give callers or regular guests a browser link to call straight into the system. It bypasses firewalls and works with the G.722 standard for phone codecs to produce a result which is fantastic. Sometimes announcers tell us it sounds too good, the listeners don’t think it is a real caller!

The Anywhere function makes a browser to browser phone call, for better quality audio, this is important because phones are definitely competing for data now.

It uses WebICT for a point to point IP connection. The STUN (Session Traversal Utilities for NAT) Server allows it to connect through firewalls and the Opus codec gives good quality over open lines.

Phone systems are changing, major media companies are moving over to these systems. SCA, ARN MediaWorks and NZME are some of the big networks using it, either via SaaS or private PaaS.

STUN and TURN (Traversal Using Relays around NAT) Servers work hand in hand. STUN figures out where you are and TURN relays messages via voice.

Telcos are turning off the old services, so it is going to be a battle for data in the future and stations have  to be equipped for that. As well as competing with other telephone callers, phone users are also competing with the telcos themselves, for example, if you are and Optus customer using your phone in a Telstra cell area, do you think that Telstra won’t prioritise the quality of its own customers over you. That is why broadcast phone calls need a way to guarantee quality no matter what the settings or priorities of the mobile phone company are.

Media Technologist & President of Technorama, John Maizels

This is a very complex topic, because there are a squillion variables that come into play and mostly we have absolutely no control over them.

Digital services have been around for forty years or more, but pre-NBN some of the best phone quality came via good old POTS (Plain Old Telephone Service ) lines - real analogue phone lines, or the digital equivalent, designed to interconnect POTS lines and not affect the signal. 
We haven't had true analogue signals between telephone exchanges for quite a while.  Those connections have been almost universally uncompressed 4kHz bandwidth, occupying a 64kbps channel for yonks.  However, the ‘last mile,’ the connection between the exchange and the office/studio/home has been good old copper wires.  In most cases, that gave a really good result.  When connected to a console via a decent digital echo-cancelling hybrid (good examples:  a Gentner DH20, the JK Innkeeper series, and the Telos Hx1) you get very good results to air. 

But we've progressed and most connections these days are fully digital, one way or another.  You'd think that would lead to a better result, wouldn't you.  It's digital, so what could possibly go wrong?


Voice Over IP services started appearing commonly in the 1990s, and many people had VoIP connections at home.  Unfortunately the desire to get more services into limited bandwidth, or to put lowest demand on dial-up or low bandwidth internet services, led to use of audio codecs that might have sounded OK in the lab but were pretty diabolical in practical use.  Many of the early codecs simply threw away bits rather than the more complex techniques we know today.  Distortion, muffled calls, and noisy conversations happened too often.

The challenge with those services from a user point of view is that it's generally impossible to turn the knobs that affect quality.  You got whatever the phone company had set in the connection box (Analogue Terminal Adaptor, or ATA) and if those settings were suboptimal for your use, the call would sound like crap.  Often the call would sound good in one direction and awful in the other direction, or the call quality would depend on who called whom.  Some users have been able to log into the box and adjust the arcane parameters, but most phone companies don't let you do that because you might actually make things worse.

For most users, the audio quality of phone services provided over NBN is still entirely dependent on the ISP and the box they give you.  It's digital to your premises, with an analogue phone port on the back of the router.  Is that bad?  My personal experience has been very good - an analogue phone to analogue phone connection via NBN can be truly excellent.   This is the service provided to many community stations, and if the panel connection is via a good hybrid, the on-air quality could be excellent.  The best thing about the NBN service, is that the quality is unlikely to change no matter where the other end of the call is... from next door to across the country, the call will be as good as the phone at the other end.

Mobile phones add an entirely different level of complexity.  The codecs used on GSM are designed to minimise bitrate.   Depending on the codec - and again, you have no control over that choice - the quality might be good or bad.   At the worst end of the scale, different brands of phones might use different codecs, leading to a situation where the audio has been coded multiple times... and that NEVER helps.  And then there's the signal path back to the base... we all know how a call sounds when the caller's signal is marginal. Anyone who has 'WiFi Calling’ fully enabled on their phone, and is connected to a decent WiFi service, is substantially bypassing the tower network and sending audio directly back to the telco's entry point over IP.  Not only does that eliminate the bad-signal effect, it might well lead to automatic selection of better end-to-end coding.

Once you get to real data connections with client-driven audio, the game can change a heap in two ways:

    - between two digital clients (eg:  Zoom to Zoom), the audio connection is full duplex, in that the input and output signals never have to be mixed.  This makes a heap of difference at the console connection end, and the software can take the place of a hybrid.  The echo-cancelling ability of the best software can be just brilliant.  Zoom, GoTo, Skype and Jitsi all work wonderfully, and the interface might take no more than a line in/out connection between a PC and the console telco channel.

    - many services offer direct dial in connections from a phone line, with numbers available for many countries.   So instead of calling your studio's local number, the caller can dial into the conference client.  There's no way to tell if the call will be stable or interrupted - you take your chances, and you're subject to many factors that you can't control.   Conferencing systems can combine many callers on-air at once, and the software sorts out all the problems of cross connections and mix-minus, which may be an advantage for interviews with multiple remote contributors.

As always, the quality of engineering into and out of the console and the PC audio interface is paramount.   No laws of physics have changed since radio began, and it's absolutely vital to ensure you manage gain structure, noise, distortion, impedances, and cabling to get the right result.  But nothing that is too onerous, there are plenty of USB audio interfaces that will do the job with balanced lines and plenty of headroom.

So there you have it. There are many aspects to the issue of good quality phone content, and I hope we have uncovered most of them, thanks to the experts.

We welcome more experiences and opinions on this issue in the comments box below, or to

Main photo: Wilko and Courts from Hit 104.7 Canberra using NextGen and PhoneBox in their home studios.



About the Author

Steve is the founding editor of this website.

He is a former broadcaster, programmer, senior executive and trainer who now runs his own company Ahern Media & Training Pty Ltd.

He is a regular writer and speaker about trends in media.

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Darren Moss
27 May 2020 - 10:08am
Great article, it's good to hear what everyone is doing with phone calls during remote shifts.
Anthony The Koala
27 May 2020 - 12:53pm
This article indicates that performance between the radio station's panel and the person's telephone is affected by the performance of the network beit IP and/or the 3G or 4G network.

May I also add my listening experience to talkback radio whether 2GB or 2BL (ABC702).

* Talkback callers using a speaker phone instead of talking directly in the phone's microphone (interestingly former PMG/Telecom Australia/Telstra refer to as transmitters). The effect is very mumbling, that is cannot discern what the caller is saying.
* Talkback callers whose phone transmitter (microphone) is the carbon microphone and the carbon microphone is on its last tracks. Poor frequency response and the sound of crackling are symptoms of a poor-performing microphone.
* Talkback callers using a handset DECT phone whose battery is almost flat.
* Talkback callers using a mobile phone with a weak signal strength. The presenter asks the caller if the caller can change the phone's direction and/or location in the house in order to increase signal strength to the mobile phone.

Sometimes it is not necessarily the phone network issues, but a problem in the caller's phone.

However, why can't a radio station's talkback switchboard be capable of handling 4G calls? Why 4G? From my experience of using 4G, a 4G user to 4G user phone call sounds clear and has a better audio fidelity than a POTS audio standard. To illustrate a 4G call between my friend in Perth WA and myself in Sydney NSW sounds so clear compared to a landline call between two POTS phones.

Thank you,
Anthony of practical Belfield
29 May 2020 - 9:36pm
Three new high speed residential plans have been introduced on the National Broadband Network (NBN), which fare available to retail service providers (RSPs) in response to increasing customer demand for higher speeds. A Media Release from Communications Minister Paul Fletcher says:

The new wholesale bundles include Home Fast offering speeds of up to 100/20Mbps, Home Superfast providing up to 250/25Mbps speeds and Home Ultrafast with a download range up to 500-1000Mbps and 50Mbps upload.

Minister for Communications, Cyber Safety and the Arts, the Hon Paul Fletcher MP, said the launch of ultra-fast services demonstrates the network’s upgrade potential and NBN Co’s focus on innovation and lifting digital capability.

“The launch of these plans is evidence of the NBN’s substantial capacity and flexibility to deliver services to meet the current and future needs of its users,” said Minister Fletcher.

“The new Home Fast plan provides speeds of up to 100/20Mbps and is available across all NBN fixed line technologies. It provides an alternative to the existing 100/40Mbps plan at a lower wholesale cost. This means around 10 million homes currently able to connect to the fixed line network will be able to access download speeds of up to 100Mbps more affordably.”

These higher speed plans have been developed in consultation with RSPs and provide competitive price points for RSPs to market services to customers. They are intended to support households with heavy data download demands, including gamers, large families and homes that have five or more people who often use home broadband simultaneously.

The Home Superfast and Home Ultrafast products will be initially made available to the Fibre to the Premises (FTTP) footprint and portions of the Hybrid Fibre Coaxial (HFC) network. NBN Co is progressively upgrading parts of the network so that more Australians are able to access these higher speed tiers.
30 May 2020 - 7:58am
There is no such thing as an analog phone connected to the NBN. New NBN compatible landline type phones produce a digital signal for the modem. If you try and use a real analog phone it will not work. It must be connected via an Analog Telephone Adaptor box, which digitises the from the phone and turns the signal from the NBN into analog. This box is then connected to the analog phone itself.

The NBN comes in the following flavours:

* Fibre to the Premises which is not affected by the amount of traffic between the local telephone exchange and the household. The fibre to the curb is almost as good as well.
* HFC which uses the old cable TV cable can be affected by the amount of traffic
* Fibre to the node is affected by the amount of traffic and often low normal speeds.
* NBN wireless is used in towns of less than 10,000 people via what looks like a UHF TV antenna is traffic dependent
* NBN Skymuster satellite service to remote areas and areas not serviced by the above. It has speed restrictions and monthly data limits.

Between the premises and the radio station there is no such thing as audible crosstalk in the NBN. Any cross talk causes errors which can cause dropouts.

You are correct about the use of the mobile phone system and overloads, particularly in emergencies and at mass gatherings such as large sporting events.
Anthony The Koala
30 May 2020 - 2:20pm
To add to Mr St John's comment on connecting a phone to the NBN, one can add an existing POTS telephone to a port on any of the network termination devices ('NTD') connected to the NBN.

Without enumerating all the inputs to an NTD, typically there is a data port for connecting a computer and an analogue telephone input to connect a POTS phone. Each of the NTD's ports may have different descriptions and colour codes for connecting the computer and phone.

The phone port on the NTD is for the old POTS phone. The signal at the phone port converts the audio to digital and then signal for transmission over the IP network via the VOIP (P for protocol). It is by law that tone (DTMF) dialling is the method for calling another telephone user and for responding to an automated switchboard delegation device - the one that says "...if you want general enquiries press 1...for payment issues press hear these instructions again press the # key...",

For rotary dial telephones, a pulse train produces a train of pulses according to the number dialled. A phone can be answered but dialling out is not possible because the NTD handles DTMF dialling.A pulse-to-tone converter such as a "DialGizmo" connected between the phone and the NTD allows DTMF dialling.

Moreover, the phone port on the NTD is also required to handle the voltages that is on the 'old' POTS system.

Thank you,
Anthony of exciting Belfield
2 June 2020 - 3:38pm
Anthony. The mobile phone networks are a mix of 3G, 4G and a tiny amount of "5G". Firstly to get 4G the caller has to have a 4G phone. If the mobile phone tower is not equipped with 4G transceivers, the phone automatically switches to 3G and this is indicated on the phone screen. Remember that at the mobile phone tower, the signals are connected to the fibre optic network to the closest telephone exchange. The studio equipment is usually connected via the NBN to the telephone system fibre optic network.

DECT and mobile phones use digital signals in the air. Digital signals contain extra data for error correction. When the signal is very weak or the battery is nearly flat the error correction fails and the phones usually mute just like DTV, and digital radio.

Carbon microphones were only in those wooden boxes on the wall and the rotary dial phones. The carbon microphones sometimes sounded bad so the user would bang the handset on a hard surface to redistribute the compacted carbon granules. Those microphones required 50 VDC to operate, where as Piezo microphones do not require any voltage except for a following amplifier. Piezo microphones have been used in all newer phones including cordless and mobile phones. Banging these handsets does not improve the sound, it just causes damage.

Modern phones contain a sound compressor so the the sound signal is the same volume if you shout or whisper.

All phone calls on the mobile phone network and via the NBN are not only converted to and from digital but the data is also compressed to reduce the data rate to allow more simultaneous calls on an individual cable. The compression algorithm has to be the same in all phones otherwise it cannot be decompressed at the other end. All POTS connections are converted to digital at the telephone exchange. Fibre Optic cables carry signals by flashing a laser on an off according to the data bits.

A large proportion of the population does not have Fibre to the premises or curb and HFC NBN connections, so they will not be able to get these faster speeds mentioned above. Is the Minster saying that the NBN is replacing Fibre to the Node to Fibre to the Curb or Fibre to the Premises which was the original design for the NBN?! The extra speed comes from using different coloured lasers on the original fibre optic cable. Copper wire will not allow light through the wire!

The NBN is replacing the POTS system and the NBN is soon to complete it's national rollout.

Both the rotary dial phones and the pushbutton types using multi-frequency dial tones will not work on the NBN. I tried to connect an older cordless phone to the NBN. It would not work and the ISP's solution was to connect the old phone to an ATA which is then connected to the phone input on the modem. The ATA cost about the cost of a pair of cordless phone. So I bought a NBN compatible set of cordless phones instead. Problem solved.

The NBN compatible phones send a digital signal to the modem phone input this includes the sound and any key presses. The internal microprocessor recognises which key is depressed it just sends the appropriate number in a designated data packet to the ISP for conversion to an address for the requested modem.

Any analog phone must be connected through an ATA (mentioned above) to convert the MTDF code to the binary number mentioned above. The ATA also has to digitise the sound signal and also convert the incoming sound data back to analog sound signal. The ATA also has to recognise an incoming call and produce the ring current so that you can hear the phone ringing, and to recognise when the handset is picked up to send a data packet to be sent to the ISP to start the voice connection. It also has to provide DC power to run the phone from a plug pack plugged into the power point.

Also there is no DC voltage on the phone input to the modem.

The NTD is the connection between the street and the modem. The phone is plugged into the modem along with any computers/Tablets. Thus the NTD is the physical connection between the internal wiring of the property and the connection to the street.

Lastly, I would like to add that if there is a power failure in your street, and you have fibre to the node and HFC, the phone and internet will both fail after little while. If the power fails for your suburb or town not only will the phone and internet fail, also will the mobile phones as well. I have experienced just that.
If you have fibre to the premises and fibre to the curb, with battery backup in the NTD the phone and internet will continue to work, because telephone exchanges have back up power, typically diesel generators. They kept all the POTS phones going, which is lost because fibre optics is made of glass and will not conduct electricity to the the user.

This is why broadcast radio is essential for emergency messaging in disasters.
Anthony The Koala
2 June 2020 - 10:48pm
Dear Mr St John,
Two points - (1) Power failures on the NBN and (2) Connecting old analogue phones on the NBN.

(1) Power failures. I have written elsewhere on this site about what happens with a power failure on the NBN. I wrote this in the context of what would happen if a radio station's IP connection failure if it is using the the internet for general web communications and/or using the NBN for transmitting and/or receiving audio via IP streams.
In sum: if there is a power failure for the following connections:

FTTP - fibre optic connection. If there is a power failure in the street, your NBN connection fails. The laser light will continue to pass through the fibre optic cable. In order to continue operating on the network, a fully charged 12V 7AH SLA battery will keep the NBN service up to 5 hours. Such a battery will fit in the FTTP box. Larger capacity batteries will have to be externally connected. This keeps the FTTP connected for much longer under a power blackout.

FTTN - fibre to the node. Power is supplied from the streets. Located in the street, the box should have standby batteries. Generally power is supplied from the street. In case of blackout, the street box's batteries should supply the power. If the standby battery fails, there is no NBN connection.

HFC - hybrid fibre connection. If power to the HFC NBN service goes, no external backup source is provided. Once the HFC has a power failure, there is no NBN service.

FTTC - fibre to the curb. A fibre optic cable runs past your house/premises. A node consisting of four connections is located in the pit. A copper cable runs from the pit to the house/premises. NOTE - the power to the pit is supplied by the house/premises. If the power fails in the house/premises, there no NBN. BUT if your NBN box and/or modem has an emergency battery/batteries in your premises/home, you can can continue to use the NBN for a specified number of hours. NOTE again - the power supplied to the FTTC is supplied by the house/premises.


Note: for the FTTC the article says that no power backup is possible during a power blackout. Prima facie that it contradicts what I said above about FTTC. The FTTC box does not have space for a spare battery. However, an INVERTER with UPS with 240VAC output may well provide backup. Do your research on 240VAC power supplies with inverter capabilities.

(2) Connecting old style phones to the NBN. Generally you can connect an old style telephone known as a "LEGACY TELEPHONE" to the NBN.


When talking about phones connected to the NBN, it is NOT about connecting broadcast-quality sound. Broadcast quality sound is sent via the UNI-D ports or network port and/or wireless wifi port of the smart modem.

Even if you have an NBN box, your phone provider will not want you to connect the legacy telephone to the NBN's NTD (connection box). The phone provider will want you to connect the phone to the smart modem connected to the NBN box.Check with your internet/telephone provider.

The NBN box is required on the FTTP and FTTC connection.

A rotary dial phone will only receive phone calls, while a DTMF phone can receive and transmit calls. Rotary phones which produce decadic pulses can only answer phones BUT not dial out. A pulse-to-tone (DTMF) converter connected between the rotary dial phone and the 'box's' phone port to operate the rotary dial phone over the NBN.

Be also careful of nomenclature is used to connect a legacy phone to the NBN equipment. IT IS IMPORTANT THAT DEPENDING ON THE PHONE PROVIDER, AND NBN TYPE CONNECTION, THE PHONE IS CONNECTED ON THE NBN BOX via the UNI-V or on "another" port on the telephone/internet provider's gateway or modem. The gateway or modem is provided by the telephone/internet provider. The "another" port may be described by the colour of the designated connection.

Anecdotally, my friend lives in Strathfield and is connected to the NBN via FTTP. Their premises has a pre-NBN Touchfone T200 which was made around 1990. The Touchfone T200 is a phone that produces DTMF tones and is connected to the FTTP apparatus.

Terminology of what is an NTD or connection box or smartmodems appear to be loose. It depends on your telephone/internet provider on how the phone and computer are connected to the NBN.

Telstra's smart modem don't talk about legacy phones connected to the UNI-V or ATA. Instead they may describe a legacy phone connection being connected to the green port or the grey port.

Where to connect your analogue phone to the NBN apparatus.

FTTP - UNI-V port of the NBN box, source, page 2, 2nd column According to the 2nd page, the UNI-V supports all the protocols ofthe G.729, that includes DTMF phones described earlier.

Alternatively, again check the current requirements of your telephone/internet provider. They may prefer you to use their smart modem and connect the legacy phone to the smart modem rather than the UNI-V.

FTTN - no NBN box in the premises. The telephone/internet provider supplies the smart modem, source, The smart modem is connected to your former landline copper wire which is then connected to the FTTN box.

HFC - connect the NBN's box's uni-d port to telphone/internet provider's gateway or smart modem. Follow the telephone/internet providers to connect your phone to the appropriate connection. The connections from the telephone/internet provider's gateway or smartmodem may well be denoted by the colour of the connection than its formal name. The instructions may say to connect the legacy phone to the green port.


FTTC - nbn connection box's data output uni-d is connected to the input of the telephone/internet provider's gateway or smartmodem. Follow the instructions given by the telephone/internet provider. For example, Telstra's video instructs its users to connect the legacy phone using the grey-coloured cable to the green port.


We have seen how to connect a legacy telephone to the NBN. NOTE we are not talking about setting up the NBN for broadcast quality audio which goes to a number of data connections.

For connecting the legacy phone to the NBN, the UNI-V port provided by the NBN's connection box may not operate with legacy phones.

The method of connecting the legacy phone to the NBN depends on the particular telephone/internet provider's requirements. It may mean that a legacy phone is connected to the telephone/internet provider's gateway or modem and NOT the NBN's UNI-V connection box.

If the telephone/internet provider says to connect the legacy phone to the smart modem, the legacy phone will not work when connected to the NBN's box's UNI-V connection.

Legacy telephones will operate on the NBN provided that the legacy phone has DTMF signalling. For example late 1980s 800 series with tone dialling, Touchfone T200, Touchfone T400 and so on.

Old rotary dials will require a pulse-to-tone (DTMF) such as DialGizmo to be able to dial out.

Note: A phone specifically designed as a VOIP phone is not an analogue phone and is NOT connected to the NBN's box's UNI-V port or the telephone/internet provider's smartmodem/gateway. Check with your telephone/internet provider.

Thank you,
Anthony of researching Belfield
4 June 2020 - 1:51am
I do not believe all that the spin doctors at the NBN tell you. I have seen the batteries in the Fibre to the Node street boxes. Just remember that there must be millions of them as there they cannot be more than 900 m of cable apart. They all contain lead acid batteries as do NTDs for FTTP and FTTC which are optional. The batteries only last a few years. I cannot see them being reliable in the long term. I wonder what the replacement cycle will be from the NBN which is supposed to be sold to a private company!
The example I gave above was an electricity outing of 6 hours in an adjacent suburb which also contains a mobile phone repeater and FTTN and the only way I could get contact was to drive there. Makes it pretty useless in a disaster which typically will last much longer than a few hours.
I was connected to FTTN in the second half of the year. The modem supplied did not have the Uni-V connector on the modem, only a phone socket which definitely did not work unless it was NBN compatible phone and or via an ATA. The ISP has to specify a SIP address for the phone from the modem.
Unfortunately only a select few have been given fibre to the Premises, and the very last installs fibre to the curb, the rest of us in towns and cities >10,000 are lumbered with Fibre to the Node in which the NTD is the original small box with just some connectors in it between the old phone wire in the street and the internal wiring.
4 June 2020 - 1:32pm
The Bateman's Bay bushfires burnt out the ABC local radio/Newsradio transmitters on the top of Mt Wandera. It is surrounded by forest. Who would like to take a fuel tanker in to power the generator on the site for not only the above but also Wireless NBN, all TV, commercial FM radio, mobile phones and two-way radios for the emergency services and the electricity company.
There was over 190,000 square km burnt last summer. It would be much better to have a high powered high frequency DRM transmitter in the centre of Australia to transmit emergency warnings and information including maps and detailed instructions including data for vehicle navigation systems from a location without physical threats. The DRM/DAB+ transmission standards include that ability to specify the emergency location and wake receivers in that location, select the emergency warnings, wake the listeners and say and show the emergency details.
For the times where there is no emergencies this transmitter could radiate ABC NewsRadio and ABC Grandstand live.
Anthony The Koala
4 June 2020 - 2:26pm
Dear Mr St John,
This is an implication for broadcasters using the NBN for the distribution and input/output of broadcast content. It also applies for the telephonic side for business and residential. It is also an issue of media commentators who peddle a particular technology.

I fully concur with you that SLA batteries will only last a few years. So if your FTTN box in the street's batteries are old and there is a blackout in the street, your NBN FTTN connection is impotent, kaput. The NBNCo who own the FTTN distribution equipment should have a maintenance program to test and replace the SLA batteries.

In addition, for HFC, no power, you're NBN HFC connection is kaput.

Lesson: for broadcasters and businesses who live in areas where they served by FTTN and HFC can at an extra cost have a fibre optic cable to the premises.

Broadcasters will certainly not want to have 'dead air' when there is a power blackout due to the NBN not operating. Contact the NBNCo and/or telephone/internet provider if this service is available.

Whatever kind of NBN connection, the FTTP (premises) and FTTC (from pit and fire cable), FTTP is the best then FTTC because you can supply the backup power whether by SLA and/or UPS/inverter. One can assume that the radio station has backup generators to prevent 'dead air'.

Don't let commentators tell you that "wireless" is the future of fast broadband. When the NBN commenced on the 9th April, 2009, all connections were meant to be FTTP.

The commentators, particularly on 2GB were pushing for wireless as if it was the panacea. I cannot speculate whether these commentators were knowledgeable on the issue or were being fed the line from vested interests. The 5G system did not exist.

Even then if too many people connect on 5G, connection speeds would be decreasing, even if the carrier frequency of 5G is 25GHz and consequential fast speed.

The 2GB commentators peddling wireless over NBN fibre-optic cable were WRONG. In my undergraduate science degree, I was enrolled in a 2nd year science unit which amongst other issues, involved experiments in fibre-optic communications. I was asked to explain in an assignment that the limitations in bandwidth in a fibre optic communication system was not due to the laser light, but due to the LIMITATIONS in the electronics between the receiver and transmitter. I topped that course.

Laser light operates on a higher frequency than wireless even 5G. Thus laser light can theoretically carry much much more information/bandwidth than "wireless" that was being peddled by 2GB commentators even pre 5G.

Consequently if there were to be improvements in the area of increased bandwidth in the interfaces on both ends of the NBN fibre optic cable, the NBN fibre-optic system would be future proofed. The reason: light carries more information than wireless even 5G and 5G may not be the panacea if more people are connected to 5G.

Finally, it is also a lesson about the dissemination of ideas by media commentators, not only about the NBN but any other concept. When it came to the NBN fibre optic, I don't believe the media commentators especially on 2GB know about the technical differences between fibre-optic and wireless communication. They certainly did not understand anything about bandwidth, especially before 5G existed.

Consequently it raises the "alarm bells" that if these commentators don't know about fibre optic versus wireless, where are these commentators getting the ideas? To put it another way, whatever concept is being discussed on air, is that concept coming from vested political or ideological or economic interests?

Anthony of analytical Belfield, and YES I do listen to 2GB and enjoy it.
5 June 2020 - 1:47am
You missed the point of this article. It was generated because of the lockdown for the Covid-19 virus. Announcers doing their program from home linked via the NBN back to the studio means than the chances of using the NBN's FTTN or Wireless NBN are high at the remote end. The studio end there is a better chance of FTTP. As a result the announcers can still be unobtainable if there is a power failure affecting the NBN. As I have pointed out if the electricity failure is widespread enough it can also stop the mobile phone/broadband system as well.
Remote broadcasts do not use the phone function except for newsgathering. Instead there is specific devices which take the microphone signal from a professional microphone, digitise and losslessly compress the studio quality signal, split it into time coded data packets and send it via a modem as a data signal not a VOIP signal. The end result is broadcast quality not telephone quality. When the data packets arrive in the studio they are not necessarily in sequential order so the data must be stored and sorted back into sequential order. Also the data rate used is limited by the ISP's plan not the low data rate used for VOIP.

You cannot use fibre optic to portable equipment or in cars. Broadcasting to all but a small audience is much cheaper for the broadcaster and the listener regardless of whether it is 3 - 5 G. Remember that 5G in its fast mode requires repeaters every 900 m or more often if there is obstructions. Hardly practical for listening in cars particularly outside of cities. Since the mobile phone coverage area per base station is much smaller than for a broadcast station which leads to patchy coverage and many more base stations to build and service. The base stations have to be connected to telephone exchanges by fibre optic cable.

Lastly be realistic about power failures in the NBN. They cannot be fixed instantaneously because a technician will have to drive to the site and connect a portable generator which takes time and stay there until the electricity supply is restored. I cannot see how the NBN will spend the money to keep the many thousands of batteries within specification for the chance there will be a black out particularly if it is eventually sold to a private company.

Increasing the bandwidth of fibre optic was demonstrated in rural NZ a few years ago. They used different coloured lasers each carrying 100 Mbit/s and at the other end dichroic filters and phototransistors. So if you use 10 colours you get 1 Gbit/s.
Anthony The Koala
6 June 2020 - 8:08pm
Dear Mr St John,
I may not have necessarily missed the point of the article.

True, that this article may apply to broadcast content from outside the studios such as the presenter's home, what I wrote still applies to radio stations and even presenters who conduct their broadcast at their house. One, the power from the presenter's house may fail in the same way that the power supply may fail at the business/radio station. Two, while FTTP or if you are in the radio station ghetto of Saunders St Pyrmont, FTTB which is a fibre optic cable to the building.

But I don't have account of all radio stations in Australia which use the particular NBN technology to receive and transmit audio material AS WELL AS other telephonic and internet services. Note that in addition to radio stations, this may be userful for other kinds of businesses that use high speed internet. It may include video post production studios who communicate and exchange their 'content' over long distances. It may also include telemedicine especially medical imaging. While the hospitals may have high speed NBN, doctors who diagnose images may well be in their surgery far away from a hospital and dare I say it, possibly not close to a FTTP NBN connection, that is the FTTP NBN does not go past the surgery.

Nevertheless knowing the nature of the NBN connection whether it is at a radio station or presenter's residence is necessary to minimise the risk of "dead air"

When you said about "being realistic" about addressing the power failure s on the NBN, you are correct. I suggested a regular maintenance plan for the FTTN batteries. It really is bad planning when SLA batteries are used but when the SLA's need replacement, the management will not want to implement it and resort to going to an emergency generator at the FTTN box.

In my opinion, it is poor risk management by management to set up an temporary generator at a faulty FTTN site because it takes time respond to the fault and to set up. It is a perfect storm with a power failure and a medical emergency at the time that the FTTN goes out of order.

In respect to the speed of communication over a fibre optic cable, speeds of up to 10Gigabytes per second have been achieved with one laser on either side of the fibre optic cable. Yes it is ethernet over fibre-optic technology as demonstrated at and is being applied in the City of Adelaide in conjunction with a telecoms provider, You don't need several lasers on one fibre cable to achieve gigabit speeds.

I agree with you on the nature of 5G equipment and the requirement that 5G transceivers are installed every 300m. Nevertheless if one is connected to 5G, the 5G may well be hogged and speed lowered if too many people are logged on to the 5G network. In addition, the frequency of 5G will not penetrate a premises as well as 3G and 4G.

Furthermore, in the 3rd last paragraph of your comment, I never envisaged FTTP on mobile transportation. That would be physically impractical.

Thank you,
Anthony of exciting Belfield
11 June 2020 - 1:57pm
Soon there will be no analog phone lines working in Australia. Whilst those who are using Skymuster Satellite NBN can keep their phone lines, it is not economic for Telstra to maintain them. The only non NBN option will be an expensive satellite uplink and hiring of time on Optus or Intelsat satellites to your own earth station will be the only way to avoid the NBN!
All mobile phones' base stations are connected to telephone exchanges by fibre optics as are connections between exchanges and to ISPs.
The satellite base stations for Skymuster are also connected via fibre optics to telephone exchanges.
I would expect that most radio stations would be connected by fibre to the building or premises being big users of data. It is the remote which is the variable.

Ten Gbit/s would be useful for TV stations but radio doesn't need anywhere that data speed after all most commercial radio programs are now being broadcast at 32 kbit/s using HE AAC compression. Into the studio higher data rates are required to prevent poor sound.

The current so called 5G is only faster because it is in a new vacant frequency band. To get the very high speeds touted the 26 GHz band is required and is not in use in Australia. That is where the repeaters are 900 m apart not 300 m. At that spacing there will not be enough users to overload a repeater and fibre optics must connect them to the telephone exchange.

The NBNCo warns that the system cannot be relied upon during blackouts. As for risk management, they are not promising to have a back up generator at satellite ground stations let alone the huge number of FTTN cabinets.
NBN recommend using the mobile phone system which isn't power backed up either! As I have already experienced.
Anthony The Koala
11 June 2020 - 5:58pm
Dear Mr St John,
Thank you for your reply.
It is indeed very interesting that the telephone exchange still plays a part in intercommunications between mobile phone stations (towers), Skymuster base stations and even between telephone exchanges! Apart from PMG/Telecom Aust./Telstra technical and engineering personnel, TAFE students in the study of electronics industry even in the 1980s were learning about frequency division multiplexing used in groups and supergroups between exchanges.

Going into history, the Sydney-Melbourne coaxial cable of the 1960s with its grey hut repeater stations. Let's not forget that the cable went through Canberra, Gundagai and Wagga. The cable was not one cable but several coaxial cables. It was built primarily for the ever-increasing demand for interstate and intercity communications.

Source: .


Based on the diagram, there is no indication of which cable was used for broadcasting, particularly high-bandwidth television as exemplified by the broadcast of Don Lane and Graham Kennedy between GTV9 and TCN9 in 1963.

In the context of broadcasting equipment, frequency division multiplexing was applied in the transmission and reception of various signals in the Philips LDK5 television camera: The cable was one core, carrying 0 Hz = power to the camera, remote control signals eg iris control, communications between the camera operator and the control room and of course the tv signal.

Anyway, I digress.

The 10Gbits cable may well be useful for TV broadcasters. In addition such high speeds are used in video post production including TV and movie editing.

Importantly, the issue discussed at the origin of this article suggests to me that 10GBits is germaine for broadcasters in controlling talkback calls precisely and remote-controlling of broadcasting equipment because of reduced latency. Latency is an issue when doctors are operating using robo-surgery techniques. An extremely high bit-rate is a boon for all!

When it comes to 32kbs broadcasting using HE AAC compression, perhaps my ears are sensitive to higher frequencies, as in earlier discussions on this site, I have noticed anything even less than 48kbs on DAB+ one could hear that disturbing tinny sound when music containing high frequency components from cymbals and even vocals containing high frequency components is present in music content.

It does not happen all the time, but my theory suggests that the source files are recorded at low bitrates using lossy compression. So in a system of digital playback -> radio station panel -> transmission -> reception, you have a system of lossy decompression at playback -> re-encoding/transcoding at radio station studio and/or transmitter -> decompression at listener's radio. The tinny sound is a result of successive removal of redundant information from a lossy compresion system and the "attempt" (sorry for personifying an inanimate system) to remove redundant information during compression.

In your second-last paragraph, I will "await" the results of users' experiences of upload and download speed when the 5G transmitters are 300m or 900m apart when demand for high-bandwidth 5G.

In your final paragraph, I find it ironic that today we need an additional mobile phone in times of blackouts on the NBN. That never happened when your "old" telephone exchange had banks of 48V DC batteries batteries connected by very thick Cu buses. The phone system operated during blackouts.
Today's NBN is a bouillabaise of different technologies where FTTP, FTTB and FTTC can be immune to blackouts by using backup batteries and/or UPS/inverters while those on HFC or FTTN don't.

Thank you,
Anthony of thinking Belfield
13 June 2020 - 12:44pm
To maintain sound quality the sound should be digitised to Audio Engineering Standards 3, 5 standards and remain that way. It is allowable to use lossless compression for storage and studio - studio links. This means no MP3 playbacks! The only time lossy compression can be used is in the DAB+ or DRM encoder which will use HE-AAC V2 or xHE-AAC lossy compressors. The xHE-ACC compression sounds a lot better at low data rates. It is a commercial decision by the broadcaster as to what transmission data rate they use. Each Australian DAB+ commercial broadcaster is allocated 128 kbit/s and they can sell some of it to others. The ABC uses 80 kbit/s for its music channels.

Historically, the first TV links between Sydney and Melbourne was advertised as a microwave link, but you are correct, a coaxial cable was used. Microwave links were used a lot for long distance communications such as Adelaide to Perth. The air temp changes at dusk around The Great Australian Bight would make the system drop out despite using dual systems at different heights above the ground.
Private microwave links are still used by commercial TV networks in the Eastern States to distribute separate programs to each region. Typically this means advertising and local news inserts! Telstra have a fibre optic Digital Video Network between capital cities.
Latency is caused by excessive sharing of bandwidth. If a very high data rate is advertised, it is advertised to all users of that service, so all common sharing systems such as wireless broadband and FTTN slow down even if the peak data rates are only achievable when the channels are quiet.

For robot surgery I would only use fibre optic communications because not only do you want high data rates, but you want high reliability!

In analog frequency division multiplex was commonly used 960 telephone channels = 1 TV channel. These days in digital systems time division multiplexing is used, where the data is in labelled data packets. When this is used for sound not all packets travel on the same path so they don't necessarily arrive in sequence. Fortunately sound and vision packets have time stamps, so they can be reassembled in memory and outputted in sequence. This is why there is a delay between the source and the destination.

Lastly the analog phone system was designed to operate in emergencies with diesel generators and lead acid batteries at exchanges. It has been replaced by the NBN/mobile phone networks which has to rely on batteries which will only last a few hours then nothing! Think about the widespread fires and the security of electricity supply during massive fires which last for days. You can't take generators and fuel through fire grounds!
The NBNCo's solution to blackouts is to tell users to use mobile phones!
Anthony The Koala
22 June 2020 - 5:16pm
Dear Mr St John,
Thank you for informing us on audio standards and FDM.

To add on the early history of distribution/dissemination of TV broadcasts by microwave links, during the 1956 Olympics in Melbourne, a fleet of OB vans was set up between Melbourne and Sydney.

While we know that microwave signals travel in line of sight, it would have been very interesting to learn at the planning stage about the logistics of organising the vans' locations and the equipment required.

Thank you,
Anthony of historical Belfield
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