Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!kitty!larry From: larry@kitty.UUCP (Larry Lippman) Newsgroups: sci.electronics Subject: Re: modems Message-ID: <1870@kitty.UUCP> Date: Thu, 23-Jul-87 13:28:11 EDT Article-I.D.: kitty.1870 Posted: Thu Jul 23 13:28:11 1987 Date-Received: Sat, 25-Jul-87 11:17:47 EDT References: <426@uop.UUCP> Organization: Recognition Research Corp., Clarence, NY Lines: 32 Summary: Buy 'em - don't build 'em In article <426@uop.UUCP>, robert@uop.UUCP (Robert McCaul--The Equalizer) writes: > even with the prices plummeting, would it be cheaper to build a > modem? It might be theoretically cheaper in component cost, but you would spend a hell of a lot of time doing it. > where would i go about getting parts? > i have lots of chip catalogs that list such things as modem chips.. Assuming that you want an "auto-dial" modem, there is much more to the modem that the actual modem IC. You need a DTMF or rotary-pulse dialer, call progress tone detection, telephone line interface, and logic to handle commands and do dialing. This logic is much too complex to perform with discrete components, so it requires a microprocessor - like an 8051. As an example, consider the Silicon Systems SSI-K212 modem IC. This IC comes out with a microprocessor data bus interface - so it MUST be used with a microprocessor. While this IC has a built-in DTMF dialer and call progress tone detector, it has no telephone line interface, and still requires a rotary dial pulsing circuit. As I see it, writing the microprocessor code to make this IC work is not a trivial task. I would guess that you would require at least 500 lines of 8051 code to emulate a Hayes modem command set. > but would it really be worth it? In my opinion, no. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rocksanne|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"