Teleco Question...

From: Richard Erlacher <>
Date: Tue Nov 30 22:47:45 1999

There's actually a more precise spec for the tip and ring voltages. If you
really want it, I can look up my old textbooks and give it to you, but first
of all, the tip-ring (battery) voltage is -48 volts, where tip is close to
ground. The ring voltage is a somewhat larger AC voltage, normally at about
20 Hz centered about RING such that there's about an 80-volt positive going
pulse with respect to tip, but symmetical about RING. The actual voltage
can vary quite a bit, but at the ends, where it enters your house, tip is AC
referenced to earth. That's probably enough info for most purposes. IIRC,
the off-hook AC signal (speech) is about 4-8 volts into 600 ohms.

That's not terribly precise, but if you need better, I can dig out some


-----Original Message-----
From: Daniel T. Burrows <>
To: Discussion re-collecting of classic computers
Date: Tuesday, November 30, 1999 9:21 PM
Subject: Re: Teleco Question...

>Q1: Can anyone tell me the two tone that make up dial tone?
>330 and 440 IIRC
>Q2: What's the ring voltage (p-p) and frequency? 90Vpp? 10cyc?
>90v 20 hz
>Q3: What's the off hook and on hook line Voltage? 9VDC and 45VDC?
>about right IIRC
Received on Tue Nov 30 1999 - 22:47:45 GMT

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