Msg: 1978 *Conference*
03-17-92 10:12:14
From: DREW BLANCHAR
To : RICK HANSON
Subj: MA BELL
Rick, Here's what I've learned of the US Bell system from my years of twisting wires. 1. Only 2 wires are needed L1 & L2 or Line 1 & Line 2. The days of the third wire are long gone partially from the safety (ground that dangerous electrical instrument) and the use of the "hybrid" that allows 2-way signals while depressing the local transmission to avoid feedback and hearing yourself too loudly. 2. The voltages on L1 & L2: 48 VDC when "on hook" or sitting hung up, still enough to charge telephone equiptment and sting your finger. 6 VDC with ac when "off hook" or you're using the phone, on-line. 100-120 vac at 20 Hz for the ringing signal. When phone is on hook, very little or no DC will get used (unless designed so) but an ac signal will get through the capacitor and ring your bell or chirper or triac-triggered-light. Definitely enough volts to kick you onto your sit-down, but the company only guarantees 5ma-- enough to ring 5 bells on your line. 3. On incoming calls, you can pick up the reciever (go off hook) and anytime during the call, go on hook at your end for up to 20 seconds then go off hook again to continue your call. Like answer the phone, hear a TDD or modem whistle, hang up the phone, run to your keyboard desk, connect to the phone again (off hook) and link up with your caller IF you've done it in less than 20 seconds and the caller (or its equipment) hasn't disconnected for lack of response. This may not work in some areas no tied directly to Bell equipment. 4. When calling out, as soon as you hang up (go on hook) the connection to your phone is broken (OK give it 2 or 3 seconds) and you can then go off hook and make another call or go back to sleep. 5. Your phone seems dead? Find L1 & L2 (either inside you phone, at the connector box, or at the side of your house) and measure the voltage. If 0 VDC and 0 vac (OK there may be a little noise but look for 0 VDC) then switch to OHMS. If the resistance is infinite, it's probably a broken wire between your place and the telco box....call THEM to fix it. If the resistance in below 600 ohms AND all your phones are hung up (on hook) or disconnected, it's a short...find out if it's inside or outside because inside service may cost you $$$. 6. By the way, that 600 ohms on the line makes the central office equipment think the line is off hook. You could put a 600 ohm resistor across the line and hang up your phone and keep the party 'on hold' until you pick up your phone again....just remember to remove the resistor when done. More than you needed to know, but readily availble in industrial electronics handbooks. Don't get yourself into trouble and I refuse to accept any shared blame. --- ----- Ma Bell's Other Children