[Most of this information was originally posted in 1999 to the Circuit Cellar site but was never echoed properly to the comp.home.automation site except in very abreviated form.
I'm reposting it here, edited, since it is still timely if you're trying to use an X10 telephone module with an answering machine.]
Getting the (TR551 or TR16A) to Cohabit Amicably With An Answering Machine
Oldtimer
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The problem is that both the TR551 and the TR16A grab the line, in answering machine mode, as if they were a telephone set. This makes the answering machine think someone has picked up a phone and turn itself off. The solution to this problem is to modify the telephone responder so that it can keep the line off hook if it is already off hook because of the answering machine but render it incapable of taking the line off hook by itself.
Typical telephone line voltages before modification are:
- All units on hook 41.5 V DC.
- Answering machine off hook 6.5 V DC.
- Regular telephone set off hook 6.5 V DC.
- Regular telephone set and answering machine off hook 4.5 V DC.
- Telephone responder off hook 4.5 V DC.
- Telephone responder and answering machine off hook 2.5 V DC (stops answering machine from recording).
Experimentation with a resistance substitution box showed that 1000 ohms in series with the telephone responder lead changed these readings as follows:
- Telephone responder off hook 21.5 V DC (this won't take the line off hook by itself but will keep it off hook if it already is).
- Telephone responder and answering machine both off hook 5.3 V DC (answering machine now ignores the telephone responder but when the answering machine hangs up the telephone responder still keeps the line off hook if you have punched in your numerical password).
For the final installation I put a 470 ohm and a 33 ohm 1/4 watt resistor (in series) in series with each side of the telephone line to maintain line balance. These were installed inside the smallest Radio Shack plastic project box with the telephone line running through it.
Finally I adjusted the timing of my answering machine messsage slightly so the three beeps from the telephone responder come just after the end of the message but just before the asnswering machine's beep so the four of them sound like they're part of the answering machine's operation. Since the three beeps come before the answering machine starts recording they don't end up on the message tape and further don't trigger the answering machine VOX circuit to record them when there's a no message hang up.
To eliminate the three beeps from the telephone responder when you answer the phone yourself I only turn the responder on when we're not at home. This is handled by two sets of macros that also accomplish a lot of other things. One set includes an OUT macro that is activated by OFF on an RSS18 switch near the back door when we leave during the day and a matching IN macro activated by ON on the same switch when we return. The other set is four AWAY macros that simulate a phantom family living in the house when we're not home for an extended period of time on a trip. When we're either OUT or AWAY the telephone responder is turned on.
By the way this mod does not interfere with the blinking light function of the telephone responder.
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Topic: Getting the (TR551 or TR16A) to Cohabit Amicably With An Answering Machine (Read 49085 times)