Telephone Power for Lights? [RE-wrenches]

[Randy Richmond]

In my day job I do a lot of work with phone lines. The following may be of
interest if you are considering borrowing some current from the phone
company.

Telephone devices that present a resistance less than 5 meg ohms across the
line can not receive FCC approval. However, I have found that you can draw
up to 1 mA without causing the central office to think you phone is off
hook. Typical phone line voltage is 42 to 56 volts but it drops to about 7
to 12 volts when you phone is off hook (about 20 mA flowing). A phone has
about a 100 to 200 ohm resistance, 600 to 900 ohm impedance when off-hook.
Also, when ringing the phone company applies 90 volts AC, 20 to 30 Hz across
the line. The most they are guaranteed to ring is 5 "ringers" on the line. A
ringer is about 8K ohms of impedance across the line at 20 to 30 Hz. Some
phone companies measure the on-hook impedance and if it looks like more than
5 ringers they threaten to disconnect your line. They might also want to
disconnect the line if you draw too much on-hook DC current.

Randy Richmond, Owner
RightHand Engineering
www.RightHandEng.com
(425) 844-1291

-----Original Message-----
From: Christopher Freitas - OutBack Power
[mailto:cfreitas at outbackpower.com]
Sent: Monday, October 22, 2001 12:02 PM
To: RE-wrenches at topica.com
Subject: RE: Telephone Power for Lights? [RE-wrenches]


Hey Tom,

Yes you can recharge batteries from the phone line - I had a friend who
did this for years...  The main problem is you can not use the phone at
the same time - it won't even ring while your charging.

The phone company also does not like this idea either and may figure out
your doing something funny at your end of the wire.

All in all its probably not worth it...

Christopher Freitas
OutBack Power Systems, Inc.
cfreitas at outbackpower.com  www.outbackpower.com
Tel 360.435.6030  Arlington WA USA

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