7
TIME-DIVISION MULTIPLEXOR
2. Introduction
The Time-Division Multiplexor is a full-duplex, RS-232, 2-channel, time-division
multiplexor with an independent switch-selectable V.14/V.22-compliant
asynchronous-to-synchronous interface adapter on sub-channel 1. The composite
channel is designed to interface directly with a high-speed synchronous modem via
a straight-through cable. The unit operates by sequentially selecting a bit of data
from the sub-channel and then multiplexing it onto the composite channel. Each
sub-channel can operate at
1
⁄
2
the composite channel rate. Standard DB25 female
connectors are provided on all sub-channels as well as the composite channel.
Power is provided by an external transformer connected through J1 (Power) on
the rear of the mutliplexor. The external power transformer is UL and CSA
approved.
Front-panel LEDs include SYNC and Power. When two TDMs are in sync with
each other and data transmission is possible, the SYNC LED should be lit. The
Power LED should be on at all times.
Three DB25 female connectors are provided for connecting the modem on the
composite port (J2) and two terminals. Channel 1 (J3) can be used for
synchronous or asynchronous operation. Channel 2 (J4) can be operated only as a
synchronous channel. Channel 1 must be used as either sync or async on both ends
of the circuit for the multiplexor to function properly.
Figure 2-1. Typical Application.
Async
Terminal
Sync
Terminal
Time-Division
Multiplexor
Time-Division
Multiplexor
Modem
Modem
Host
Processor
