How much electrical current actually comes through a phone line?
You can leave an optional "tip" with Mahalo's virtual currency, Mahalo Dollars. If you are asking a difficult question that might require some research, or if you'd like a wide variety of feedback, a higher tip often leads to more answers to your question.
M$2 Answers
To ring your telephone, the telephone company momentarily applies a 90 VRMS 20 Hz AC signal to the line. Even with a thousand ohms of line resistance, this is still a bit of a shock if you happen to touch the wires, so be careful when you are touching phone wires.
Typical telephone DC resistance around 180 ohms and AC impedance is around 600 ohms. Generally the telephone central provide from 200 to 400 ohms of series resistance to protect from short circuits and decouple the audio signals.
You can leave an optional "tip" with Mahalo's virtual currency, Mahalo Dollars. If you are asking a difficult question that might require some research, or if you'd like a wide variety of feedback, a higher tip often leads to more answers to your question.
M$However, you should be aware that most phone lines have what is called a R.E.N. value of 5. REN stands for Ringer Equivalent Number.
1 REN is the amount of current required to power a standard phone of the old-style. Most devices such as answering machines or modems should have a REN rating somewhere. You can attach more than one device to the line so long as you don't exceed 5 REN.
If you are planning to use the phone line as a power source, you should be aware it is illegal to do so.
Otoh, I've installed my own telephone extensions (which is also illegal) and I can say that there is not enough current to cause a shock.
Knowledge I had from working with modems and BBSs, but you can read more here:
http://en.wikipedia.org/wiki/Ringer_equivalence_number
You can leave an optional "tip" with Mahalo's virtual currency, Mahalo Dollars. If you are asking a difficult question that might require some research, or if you'd like a wide variety of feedback, a higher tip often leads to more answers to your question.
M$
I once put a bare telephone wire tip while it was plug in the other end in my mouth and it shocked me!
How can an 'extension phone' be illegal? Your still using 1 phone number and only 1 phone to make/receive calls.
Even if you have 50 telephones attached to 1 landline number. The only thing it will do is hear 50 phone units ringing simultaneously when somebody calls. 50 different rooms to answer that call. Up to 49 other people at your premise could possibly eavesdrop/join your conversation. So it really makes no sense at all.
When I was a kid. When PLDT was a monopoly and was the only phone company in the Philippines. They have lobbied congress making extension phones illegal. You have to pay an additional monthly charge to attach another phone unit at home. There was a law and fines, if your phone company founds out you got an extension phone. It only became a source of corruption on lineman to harass you to inspect your home to see if you got an extension phone. Its kind of silly why you have to remove and hide the extension phone when a lineman comes to visit for repairs or inspection.
Nowadays phone companies here don't care how many extension phones you got at home. For reason only 1 person can make/receive calls at a time.
The extension was not illegal, the fact that I wasn't a certified electrician or telephone company technician made it illegal for me to perform the work myself. I just didn't feel like paying someone $80 to connect a few wires to the screw terminals in the socket.
I guess I was lucky that nobody rang... actually the line was not active from the telephone company's standpoint, so no calls would have been coming through.
As far as attaching 50 phones, well you wouldn't hear anything at all... this is the point of the REN. If you have too many devices there isn't enough current to power them and they won't ring.
But yes, basically in Australia as in the Philippines, you used to have to pay for an extension but now you don't.
You would however "feel it" if you were touching the bare conductors when the "ring signal" was being received.
