Mark Lloyd wrote:
On Mon, 25 Aug 2008 15:43:41 -0500, Uncle Monster
wrote:

[snip]


EEK! Wrong voltage! The nominal DC voltage
on a phone line (on hook) is 48 volts DC.
The (off hook) voltage can be anywhere
between 6 and 12 volts DC. It's the (off
hook) loop current in milliamperes that
important. 15-36 ma is what I typically
see. The US standard ring voltage is 90
volts AC at 20 Hz unless you're on a party
line and the ringers will be of the type
that are filtered to ring at different
AC frequencies. The 48 volts can tingle
but the 90 volts will definitely bite you.
Don't strip a live phone line with your
teeth because that's the exact moment that
one of those damn telemarketers will decide
to call. If you're looking for good info
on phone systems and a source of parts, try
http://www.sandman.com/ I've purchased
phones and parts from the company for years.
Oh, the green (tip) and red (ring) wires
are the only ones you need for a standard
single line telephone as was previously
mentioned.


Loop impedance is high (IIRC 400 ohms is normal). This causes the
voltage to drop considerably when a load is applied (same as in a very
old battery). The ring voltage is low impedance.

I'll bet you don't know what an "octothorp"
is. It's a part of every pushbutton phone.
*snicker*


I thought is was an "octothorpe". Another name is "nanogram", although
I don't see that much.

octothorp / octothorpe / octathorp / octatherp

Also called a hash mark and various other things.
It has an interesting history.

As to something else pushbutton-related, how about the "A" "B" "C" and
"D" keys?

My understanding is that the letters were found
on military phones connected to the AUTOVON phone
systems that's no longer in use. I think phone
company networks use them for network control and
monitoring. I have some butt sets that have the
letter keys and some actual phones somewhere in
my collection. I was talking to someone today about
my great uncle who was a lifer in The US Army Signal
Corp. He joined when they were still using two tin
cans and a string and I'll bet he was familiar with
the AUTOVON system.

[8~{} Uncle Monster