102 lines
3.6 KiB
Plaintext
102 lines
3.6 KiB
Plaintext
|
From telecom@delta.eecs.nwu.edu Wed Jan 27 06:10:48 1993
|
|||
|
|
Received: from delta.eecs.nwu.edu by gaak.LCS.MIT.EDU via TCP with SMTP
|
|||
|
|
id AA29057; Wed, 27 Jan 93 06:10:45 EST
|
|||
|
|
Received: by delta.eecs.nwu.edu id AA10632
|
|||
|
|
(5.65c/IDA-1.4.4 for ptownson@gaak.lcs.mit.edu); Wed, 27 Jan 1993 05:10:32 -0600
|
|||
|
|
Date: Wed, 27 Jan 1993 05:10:32 -0600
|
|||
|
|
From: TELECOM Moderator <telecom@delta.eecs.nwu.edu>
|
|||
|
|
Message-Id: <199301271110.AA10632@delta.eecs.nwu.edu>
|
|||
|
|
To: ptownson@gaak.LCS.MIT.EDU
|
|||
|
|
Subject: answer machine exclusion key
|
|||
|
|
Status: R
|
|||
|
|
|
|||
|
|
|
|||
|
|
>From telecom Mon Jan 25 06:07:25 1993
|
|||
|
|
Received: by delta.eecs.nwu.edu id AA14620
|
|||
|
|
(5.65c/IDA-1.4.4 for \telecom); Mon, 25 Jan 1993 06:07:22 -0600
|
|||
|
|
Received: from world.std.com by delta.eecs.nwu.edu with SMTP id AA00657
|
|||
|
|
(5.65c/IDA-1.4.4 for <telecom@eecs.nwu.edu>); Mon, 25 Jan 1993 06:06:58 -0600
|
|||
|
|
Received: by world.std.com (5.65c/Spike-2.0)
|
|||
|
|
id AA06197; Mon, 25 Jan 1993 07:06:51 -0500
|
|||
|
|
Date: Mon, 25 Jan 1993 07:06:51 -0500
|
|||
|
|
From: jon_sree@world.std.com (Jon Sreekanth)
|
|||
|
|
Message-Id: <199301251206.AA06197@world.std.com>
|
|||
|
|
To: telecom@eecs.nwu.edu
|
|||
|
|
Subject: Answering machine exclusion : schematic
|
|||
|
|
Status: RO
|
|||
|
|
|
|||
|
|
|
|||
|
|
Hi Pat :
|
|||
|
|
|
|||
|
|
This is either for publication, or FAQ or what-have-you. I typed it up
|
|||
|
|
in response to someone's question, so maybe others will find it
|
|||
|
|
useful.
|
|||
|
|
|
|||
|
|
----
|
|||
|
|
|
|||
|
|
This is the schematic I traced for an answering machine stopper
|
|||
|
|
gadget : it cuts off the answering machine in case any line is picked
|
|||
|
|
up. Some answering machines have this feature built-in; the older or
|
|||
|
|
inexpensive ones don't. The gadget is called Message Stopper (R), by
|
|||
|
|
Design Tech International Inc., Springfield, VA. Several other mfrs
|
|||
|
|
make this kind of gadget, so this is just one I happened to buy.
|
|||
|
|
Cost, roughly $10.
|
|||
|
|
|
|||
|
|
The gadget is in the same form factor as a wall-plug-in Y-splitter.
|
|||
|
|
That is, it plugs into the wall RJ11 outlet, and has two RJ11 outlets
|
|||
|
|
on it, one marked TEL, the other marked ANS. There are two LED's, the
|
|||
|
|
green one on top of the ANS outlet, the red one on top of the TEL outlet.
|
|||
|
|
|
|||
|
|
The two outer wires of the three RJ11's are wired in parallel. The
|
|||
|
|
schematic for the center two wires is :
|
|||
|
|
|
|||
|
|
|
|||
|
|
.-------------- phone
|
|||
|
|
.-----------------
|
|||
|
|
| |
|
|||
|
|
C1 ----|
|
|||
|
|
C2 -| |
|
|||
|
|
| |
|
|||
|
|
| |
|
|||
|
|
| '----------------- answering machine
|
|||
|
|
|
|
|||
|
|
+--|<--+--|<--->|----
|
|||
|
|
| | two zeners
|
|||
|
|
+-->|--+
|
|||
|
|
two leds
|
|||
|
|
|
|||
|
|
Top led is green, bottom is red.
|
|||
|
|
|
|||
|
|
It turns out the leds are basically idiot lights. The outside design
|
|||
|
|
makes it look like the green should light up when the ANS is offhook,
|
|||
|
|
and the red when TEL is offhook, but actually, depending on the line
|
|||
|
|
polarity, only one will glow, and only when the ANS outlet is offhook.
|
|||
|
|
If a load is connected on the ANS outlet, both leds will glow when
|
|||
|
|
ring voltage comes through.
|
|||
|
|
|
|||
|
|
I could not read the zener voltage off the diodes, but I measured 11V
|
|||
|
|
across one of them when operating.
|
|||
|
|
|
|||
|
|
The theory of operation is straightforward. All telephone extensions
|
|||
|
|
in the house are in parallel with each other, and with any device connected
|
|||
|
|
on the TEL outlet. If any of these devices is offhook, the phone line
|
|||
|
|
voltage is expected to drop below 12V or so, at which point the zeners
|
|||
|
|
isolate the ANS outlet from the line.
|
|||
|
|
|
|||
|
|
It's a fairly simplistic design, and will not work in all situations,
|
|||
|
|
but it mostly works.
|
|||
|
|
|
|||
|
|
----
|
|||
|
|
|
|||
|
|
Regards,
|
|||
|
|
|
|||
|
|
/ Jon Sreekanth
|
|||
|
|
|
|||
|
|
Assabet Valley Microsystems, Inc. | Fax and PC products
|
|||
|
|
5 Walden St #3, Cambridge, MA 02140 | (617) 876-8019
|
|||
|
|
jon_sree@world.std.com |
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|