Daniel Wynalda <danielw@wyn386.mi.org> (04/04/91)
Although I'm not a bad systems analyst, I wouldn't consider myself any kind of electrical engineer. I can, however operate a soldering gun. Here's my problem: I have a single line cordless phone that I want to work on several phone lines. Ideally, this is what I'd like to do: After a flash (hangup) on the phone, I'd like a box that will listen for a tone from the keypad on the phone. This tone will select the phone line that I wish to be connected to. This box doesn't seem like it would be that hard to build, and I'm surprised that no one else has done this and marketed it. Is there anyone out there who's attempted a project like this? It is not that important that the phone actually ring when calls come in on any of these lines. I just want to be able to pick up line 3 when I hear a page for "Line 3". Without walking a half-mile. I would think a tone decoder wired to three relays could do the logic for three lines -- just press 1 to flip relay 1 on (thus forcing 2 and 3 off). This would work for all three lines. My main question in the design would be how to DISCONNECT the phone from the phone lines on flash (hangup) but still supply voltage to the phone to decode the tones. I suppose I could monitor the phone line for voltage change when returned to hook. This could disconnect the phone from the lines -- but what voltage should I feed the phone so the decoder can watch for a tone? After the tone is heard, I'd want the box to drop off the line (or ignore more tones -- because I'll have to dial out sometimes). Any suggestions? Is this a project that is feasible for a near-beginner or is there someplace I can purchase such a device?? I have had some basic electrical classes including digital circuits in college. Any information is appreciated. Daniel Wynalda | (616) 866-1561 X22 Ham:N8KUD Net:danielw@wyn386.mi.org Wynalda Litho Inc. | 8221 Graphic Industrial Pk. | Rockford, MI 49341
faunt@cisco.com (Doug Faunt N6TQS 415-688-8269) (04/07/91)
The new Radio Electronics (May, 91) has an article on building a couple of units to use your house telephone system as an intercom, that could easily be adapted to your function.