4
HIGH SPEED SHM-B ASYNC AND CARD
The High Speed SHM-B Async is an asynchronous
full-duplex 4-wire line driver/receiver. With a pair of
these devices, two EIA-232 devices can com-municate
at distances of up to 4 miles (6.4 km) and at data
speeds of up to 115.2 Kbps. In addition to the
transmitter and receiver circuits, the High Speed
SHM-B Async includes EIA-232 control-line
interfaces, status monitor LEDs, and a loopback
switch. The High Speed SHM-B Async is available in
both a standalone version (ME802A or ME802AE)
and a rackmount card version (ME802C).
The High Speed SHM-B Async is designed to operate
over a 4-wire metallic circuit. The best performance
is obtained with twisted-pair cable (see
Chapter 1
).
Most types of twisted-pair cable may be used;
however, to achieve maximum performance, we
recommend Level 4 or Level 5 UTP cable.
The High Speed SHM-B Async is designed for
maximum operator safety. There are no voltages
greater than ±9 VDC or 17 VAC present on the
circuit board of the unit. The Receive lines are
protected from potential ground differences
through optical isolators rated at 2500 volts.
2. Introduction
