# landline telephone voltage

1. ## landline telephone voltage

Is land line telephone has a particular operating voltage.

•

2. ## Re: landline telephone voltage

Yes. they feed 48 to 54 V Dc with a current limit of 25 to 35mA for phone working. For rining , they feed 50 to 75V 25/50Hz AC superimposed on the DC voltage mentioned above.

3. ## Re: landline telephone voltage

In the U.S. the line is at ≈48V with a negative ground and when ringing hits ≈90V. Tip and ring - Wikipedia, the free encyclopedia

4. ## Re: landline telephone voltage

Originally Posted by mvs sarma
For rining , they feed 50 to 75V 25/50Hz AC superimposed on the DC voltage mentioned above.
and for the voice communications, that is simply a lower voltage AC signal superimposed on the line.
When a connection between the 2 telephones is made, and current is drawn, then the DC voltage drops to just a few volts.
However please note that dangerously high voltages can appear on the traditional, old, landlines which travel long distances in the open air, including pulses from lightning which may be poorly captured by the protection installed at the switches/exchanges.

5. ## Re: landline telephone voltage

as per any standard , it might be positive ground. As per Telecom bibles, a positive grounded supply on the olden days open wire lines, helps to save copper wires from electrolytic action between the ground and the other wire, atmosphere acting as electrolyte.
Earlier designs have slowly disintegrated copper wires. then the technology had been changed to positive ground. most telecom installations across world follow this as a principle, including AT&T and many other American digital switches.

6. ## Re: landline telephone voltage

Originally Posted by encoder
Is land line telephone has a particular operating voltage.
Operating voltage usually refers to off-hook voltage.
Also depends on your telephone circuits but it works at around 6.5V to 12V.

•

7. ## Re: landline telephone voltage

the idea of feeding a voltage some where between 48 to 52 is that the phones have to work for a distance of say 4 to 5Km. Including the line resistance, and the impedance of the battery feed circuit of the central office and that of instrument itself, to drive a 25 to 30mA of DC current for proper operation, such high voltage is needed.

8. ## Re: landline telephone voltage

ringer voltage is 75V AC and there exists 45V always on the line

9. ## Re: landline telephone voltage

in electromechanical exchanges the ringing current is super-imposed on the dc. Later, in electronic exchange era some designs feed ringing alone and battery feed during ring pause periods.

10. ## Re: landline telephone voltage

In North America the ringing is 90VAC RMS at 20Hz.

•

11. ## Re: landline telephone voltage

its nice but if my phone in ideal mode then what is the power consumption..

12. ## Re: landline telephone voltage

What is "ideal mode"??

13. ## Re: landline telephone voltage

I recommend this book:

Understanding Telephone Electronics (4th ed.) BIGELOW, S. J. (2001).

--[[ ]]--