The
RSD-20, High Speed Digital Sharing Device,
enables any combination of up to four modems
and/or terminals to share a modem, multiplexor
or computer port in a multipoint environment.
It operates synchronously at 56 or 64Kbps.
RSD-20 is completely transparent to the
system and the data. It generates timing
signals internally or operates with external
clocks, either from the main channel or
from sub-channel 1. An integral buffer accommodates
the differences in clocking phases.
The main channel broadcasts information
to all sub-channels in parallel. Sub-channels
contend to transmit to the main channel
by activating RTS/DCD (V.35), CONTROL/INDICATE
(X.21) or by data transitions. A sub-channel
can be disabled automatically if it stays
active for longer than a preset time and
blocks all other sub-channels. An indicator
on the front lights for each sub-channel
when disabled by automatic circuitry. Permanent
disabling of a sub-channel is possible by
setting the front panel switches. Installation
and configuration of the RSD-20 is easy.
All necessary crossover connections are
performed internally, via a DCE/DTE switch,
and only straight-through cables are used
to connect the modems or terminals to RSD-20.
Two interface versions are available: V.35
or X.21. The unit is available as a stand-alone
or for mounting in a 19" rack.
