Rich Mintz <rmintz@ecst.csuchico.edu> (06/27/91)
I own a product from Radio Shack called the "Multiphone Recording Control" (catalog no. 43-236). That's a nice way of saying "Sneaky Phone Tap." This line-powered device is a small box with one regular, mono, earplug-type connector (plug, not socket), and one smaller plug. The larger plug is connected to the MICrophone jack on a tape recorder, and the smaller plug, to the REMote jack that older tape recorders have (not needed with new recorders that automatically turn on and off by monitoring their MIC's sound level). Once this box is connected to any extension in the house, it will automatically turn on the recorder and record a conversation (or any line activity) when ANY extension in the house is picked up, and stop recording, and go off-line, when all extensions are hung-up. When you consider the function of the signal from the remote jack by itself, it is essentially an "In Use" light, but in "signal" form (for lack of a better word). I interfaced this remote jack lead to my computer via the "external event detection jack" on my voice mail card, which is capable of detecting an open or closed circuit, intended for use with security systems, etc. Connecting the remote lead to the computer for monitoring with software could just as easily be done using one of the printer or COM port leads, etc. I wrote a little routine in Turbo C that will check the port, and report whether all extension phones are hung up or not, without having to actually pick up the phone. Now, if I need to make a call, and someone's on the line, the computer will alert me as soon as they have hung up, without having to bother the caller by continuously picking up the phone to check if the line is free. The system has worked fine for a long time, but I'm having a problem with it now. I built the "in use" light from the schematic submitted by Nelson Bolyard in article number 12352 (thanks, Nelson), and it worked fine. Unfortunately though, the Radio Shack device sends little "pulses" to the phone line when the line is not in use, presumably as some side effect of its being line-powered. For whatever reason it does this, the unwanted result is that it causes the "in-use" LED to blink constantly when the line is not in use, and to come on steady when it is. This is not only confusing to those using it as an indicator of line status, but it will also cause the batteries in the "in-use" device to be depleted quickly. Due to some earlier, unfortunate "tinkering" with the RS product, the portion of the circuit which handles the output to the MIC jack was ruined, and no longer functions. However, I distinctively remember this tendency for the device to send pulses to the line even when it was brand new. In fact, when monitoring the signal from the REMote lead with software, I have to check for a continuous 1..0..1..0..1..0 pattern to signify all extensions on hook, and a steady 0..0..0..0..0 when an extension is picked up. I have driven myself bonkers trying to fix the problem by removing and adding capacitors on both the RS unit, and the "in-use" circuit with no luck. 1) Any suggestions for stopping those annoying pulses on the line by the RS device? 2) Would it be safe (and feasible) to use Nelson's "in use" schematic, but connect the computer signal leads across where the LED is supposed to go, in order to get a true signal for the line status that won't pulse? 3) As I am only using a 2400 baud modem, a simpler, line-powered "in-use" circuit would (hopefully) not interfere with my modem, and would simplify my assembly of three or four of these units for all of the extensions in my house. Anyone have such a schematic that will work? 4) Does an alternative device exist that will simply "suck" all the line voltage away from the other phone extensions in the house when mine is in use, to prevent pickups from disturbing my modem's activities? NOTE: It may be illegal to record phone conversations with the device mentioned in this article, without the knowledge of one or both parties on the line, in your state. Inquire about applicable laws where you live before doing so. Thanks a lot, Rich Mintz Internet: rmintz@cscihp.ecst.csuchico.edu CompuServe: 71560,1142 Phone: (916) 894-3342, Chico CA
"Patton M. Turner" <pturner@eng.auburn.edu> (06/30/91)
Rich Mintz <rmintz@ecst.csuchico.edu> writes: > 4) Does an alternative device exist that will simply "suck" all the > line voltage away from the other phone extensions in the house when > mine is in use, to prevent pickups from disturbing my modem's > activities? A Radio Shack Teleprotector (43-107, $7.95) installed upstream of the remainder of the phones in your home will acomplish this. Unless you want to buy one for each phone in your house, connect a modular tee to the network interface. Plug the entrance bridge into the teleprotector and plug the teleprotector into one of the ports on the tee. From the other port run a line back to your modem. When your modem goes off-hook the remaining phones are disconnected from the line. We have had one of these devices installed at a repeater site for a year now with no problems. If your home goesn't have a network interface the teleprotector can be spliced into the line. Just remember to attach your modem line on the CO side of the device. Pat Turner KB4GRZ pturner@eng.auburn.edu