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Does NBN provide Voltage on the phone line?

Does NBN provide Voltage on the phone line?

Does NBN provide Voltage on the phone line?


I heard that the NBN doesn’t require any voltage on the phone line for internet service. Does this mean I can still use my traditional landline phone with the NBN? How does that work?

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Your Answer


Great question! You’re correct that modern NBN technology doesn’t require voltage on the line for internet data transmission. However, if you wish to continue using your traditional landline phone, you certainly can. When you transition to the NBN, the required 48V DC voltage for your traditional landline phone can be supplied through the modem’s FXS port.


Regarding the ring voltage, it’s important to note that this can vary depending on the specific hardware and configuration. According to data available, the ring voltage from a VoIP port on a router could range from 40 to 90 Vpk (Voltage peak), as specified in a Cisco data sheet for a particular VoIP adapter​1​. The ring voltage is often discussed in the context of FXS (Foreign Exchange Station) voice ports, which provide ring voltage along with dial tone to the connected devices​2​. In certain Cisco voice gateways, the FXS interface supplies either -24Vdc or -36Vdc idle battery​.


The exact voltage might vary depending on your particular VoIP hardware and its configuration. If you have a specific model of router or VoIP adapter in mind, we recommend consulting the technical specifications or user manual to find out the precise ring voltage it provides.


This means that your modem takes on some of the functions previously carried out at the telephone exchange, making your home NBN modem a crucial piece of equipment for both high-speed internet and traditional phone service.

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