SHM-B ASYNC
2. Introduction
The Short-Haul Modem Model B Async (SHM-B Async) is an asynchronous full-duplex 4-wire line driver/receiver which allows two EIA-232 devices to communicate at distances of up to 4 miles and at data speeds of up to 19,200 bps. In addition to the transmitter and receiver circuits, the SHM-B Async includes EIA-232 control line interfaces, status monitor LEDs, and a loopback switch. The SHM-B is available in both a standalone version (ME800A) and a rackmount version (ME805-C). Models ME800A-R2 and ME805-C- R2 include cables.
The SHM-B is designed to operate over a 4-wire metallic circuit. Optimum performance is obtained with twisted- pair cable (see specifications). Most types of twisted-pair cable may be used, often with little or no performance degradation.
The SHM-B Async is designed for maximum operator safety. There are no voltages greater than 12 VDC or 16 VAC present on the circuit board of the unit. The Receive lines are protected from potential ground differences through optical isolators rated at 1500 volts.
