0004133373@mcimail.com (Donald E. Kimberlin) (06/05/90)
Smith writes: >I have just gotten ahold of two (ICC MPS48) 4800 baud modems.... >.... But I cannot get it to accept any commands. >.....Does anybody have ANY information on this modem? Ian, you've got yourself a pair of a couple of real good "moldy olides" there. MPS48's have been the workhorse of many large, farflung global networks for years. The maker is Racal-Milgo, one of the Big 3 on non-Bell modem makers for years. You can try their factory at Plantation (Ft. Lauderdale subuarb, NOT the Plantation in the Keys), Florida, but they may not be interested in passing out free help. They have a LARGE worldwide service force to sell to you. Better you call around the major banks near you, like Philly and get to someone in the data network area, who get s one or two books for each of the (truly!) HUNDREDS of MPS48s they use in their big machine networks. Here are three things to start you off: 1.) These are four-wire, full-duplex private line modems. That means they work on TWO "two-wire" analog phone circuits, so hook up the "transmit" terminals of one to the "receive" terminals of the other. Those modems can send from across the room to across the ocean on such circuits, so run them wherever you want to...just give them separate "go" and "return" analog circuits. 2.) Such modems in large machine networks are for sync data terminals, and while PC clocks are getting so good nowadays you may be able to just jam async at them and seem to work for a short time, you will probably have trouble with data "slips" on long files unless you run your terminals in "sync" mode and provide interface cables that exchange clock between the terminals and modems. That means more wires in the cables than the usual 3 or so of PC usage. 3.) Such modems transmit a full 0 dBm composite data signal, and expect a received signal of -16 dBm. Their receivers are very sensitive, and can function clear down to about - 42 dBm. In the case of a short wire circuit across the room, or even across the campus, they will probably overload their receivers. You need to either get an attenuator into the analog wire circuit OR reduce the sending level (by means of internal hardware options any tech can readily identify) to - 16 dBm to avoid receiver overload, which occurs very rapidly even at - 12 or -13 dBm received signal level on them. 4.) In big machine networks, the "smarts" are all in the controller, a.k.a. DTE (Data Terminal Equipment). Thus, MPS-48s don't respond to Hayes commands from the keyboard. They're just up on line all the time and transmit whatever you send..if these are the classic "private -dedicated" line version most people have. IF they have two-wire dail-up interface boards added, they expect you to have an external telephone with an "exclusion key" transfer between voice and data, and you dial with the phone, then switch to data connection .. .or perform the equivalent with an electronic substitute. But, I doubt you have that added hard- ware in yours. If you do, the extra boards will be readily identifiable. The MPS-48s are VERY good, durable devices and you should expect good use from them. Some contacting people from large data-using firms and getting a hep technician on them should get them working for you in most any way you like. ...So what do you have? A pair of the "workhorses" from that "other galaxy" of data communications, the galaxy of the big mainframe machines; it seems to be a place dial-up PC users have heard little about, even though it sells a billion or more a year worth of those modems! Once you get a good tech on them, you'll find they are really pretty simple. Happy intergalactic datacomm!