Testing my telephone line.

Thread Starter

jmoffat

Joined Jul 18, 2012
42
Currently my house is not connected to a telephone network. I want to test all of my telephone circuits. I guess I need to send a audible tone on the wires plus some voltage to power the phone. So what voltage do I need to power a modern ( not rotary dial ) phone? I do not necessarily need to ring the the phone. I can simply plug in the phone and listen.
 

Dodgydave

Joined Jun 22, 2012
11,339
A simple 12v psu adapter ( walwart) on the incoming cable terminals will do, then measure the voltage at each telephone socket.
 

KL7AJ

Joined Nov 4, 2008
2,229
Currently my house is not connected to a telephone network. I want to test all of my telephone circuits. I guess I need to send a audible tone on the wires plus some voltage to power the phone. So what voltage do I need to power a modern ( not rotary dial ) phone? I do not necessarily need to ring the the phone. I can simply plug in the phone and listen.
Rotary or dial, they are all designed for the standard land line standards. Normal audio is -13 dbM at 600 ohms. The DC voltage is -48

Sorry about that....fat fingers. P:)
 
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Thread Starter

jmoffat

Joined Jul 18, 2012
42
Rotary or dial, they are all designed for the standard land line standards. Normal audio is -13 dbM at 600 ohms. The DC voltage is -28

Thanks to Alec_t, crutschow, Dodgydave and KL7AJ for your replies. Yes I didn't really think it through. Trying to get voltage readings from a modular outlet is difficult. that's why I wanted to just plug in a phone. This morning I put together a 24v power supply a small relay and a Zip-Link module. The relay is wired as a buzzer and the Zip-Link provides screw terminal access to a modular outlet. Plug in a phone and the buzzing can be heard from the receiver. An RJ-12 jumper plugged into any modular outlet in the system will allow me to check the other branches. I used these materials because I have this stuff readily available at work. The whole thing is mounted to a scrap of Din rail. I will take my contraption home tonight and bring it back in the morning.
 

dl324

Joined Mar 30, 2015
17,094
This morning I put together a 24v power supply a small relay
Phone companies in the US don't like you messing with things like that. Make sure you disconnect your network interface box from the phone line drop to your house.

Even if the phone line is "disconnected", it could still be live. I have a second line at my house that was paid for by my previous company. It was "disconnected" over 10 years ago, but the line still works.
 

GopherT

Joined Nov 23, 2012
8,009
Phone companies in the US don't like you messing with things like that. Make sure you disconnect your network interface box from the phone line drop to your house.

Even if the phone line is "disconnected", it could still be live. I have a second line at my house that was paid for by my previous company. It was "disconnected" over 10 years ago, but the line still works.
Did you see his first post?

Currently my house is not connected to a telephone network.
 

ian field

Joined Oct 27, 2012
6,536
Yes, all you need is a continuity test if you are just testing the wires.
Not quite - telephones are capacitively coupled, on hook - they only respond to AC such as the ring tone.

Off hook, they draw a bias current - originally for the carbon granule mic, nowadays some simple circuitry around an electret mic. There's almost always at least a dialler chip and a simple regulator that can be as simple as a Zener and resistor.

The exchange usually puts about 48V on the line.

Over the years there have been a few magazine projects for phone test set boxes.
 
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