# What is the voltage on a BT line?

## What is the voltage on a BT line?

The exact voltage drop is a function of the distance to the exchange, and the network wiring type. According to SIN 352 the average DC current in the loop and voltage across the phone will be up to 42 mA at 12.5 V (short line), up to 33.5 mA at 10 V, and will be not less than 25 mA at 9 V.

## Can I replace my BT master socket?

You cannot replace that socket as it is the property of Openreach.

Can I have 2 master phone sockets?

Re: Is it OK to have 2 master sockets on same line? Yes, leaving that set up as is should be fine. Personally I’d consider removing the bell wire if any problems start to occur.

What voltage should be on my phone line?

The POTS phone line, with all phones on-hook, should measure around 48 volts DC. This drops down to the 3 to 9 volt range when a telephone on the line goes off-hook. An off-hook telephone typically draws about 20 milliamps of DC current to operate, at a DC resistance around 180 ohms.

### What should the voltage be on a telephone line?

48 VDC
In the United States, the voltage applied to the line to drive the telephone is 48 VDC; some countries use 50 VDC. Note that telephones are peculiar in that the signal line is also the power supply line.

### Can I use the BT test socket permanently?

Leaving the faceplate off and using the test socket with a microfilter is fine. My own router is permanently connected to my test socket and I’ve had no issues. If you are happy to leave the router connected there then this will be fine.

Can you have 2 master phone sockets?

You should only have one master socker, the rest will be secondary/slaves.

Can I relocate my BT master socket?

Re: Moving Master Socket You would have to ask BT to arrange an internal shift, and they would pass the task to Openreach.

#### Does polarity matter on phone lines?

Polarity. To provide cathodic protection against corrosion of line wires, the operating potential of telephone lines is typically negative with respect to ground, and the tip side is generally close to the ground potential.