3
CHAPTER 2: Introduction
2.1 Description
The Async/Sync Fiber Optic Multiplexor is a full-duplex time-division
synchronous/asynchronous multiplexor that enables up to 12 terminals to be
multiplexed onto a single fiberoptic channel. (The mux’s normal total of six
subchannels can be increased to 12 by using channel-doubler cables, product
code EYN356.) Channels 1 through 3 can be set to operate either synchron-
ously or asynchronously, while the remaining three or nine channels always
operate asynchronously.
Various configurations can be set up to suit your specific needs:
• Up to six asynchronous data channels with one control signal per channel
at data rates up to 19,200 bps. (A control signal is the same as hardware
flow control.) This signal, input to the local unit on Pin 14 (STXD,
Secondary Transmitted Data), is transposed at the remote unit and
output on Pin 16 (SRXD, Secondary Received Data). The control signal
may require special cabling; the mux can process it only in 6-channel (not
12-channel) mode at up to 19,200 (not more) bps.
• Up to six asynchronous data channels without control signals at rates
up to 38,400 bps. (Distortion increases at async speeds above 19,200 bps,
preventing the use of control signals.)
• Up to six data channels: up to three operating synchronously at rates
up to 19,200 bps and the rest operating asynchronously, with no control
signals, at rates up to 38,400 bps.
• Up to 12 data channels: up to three operating synchronously and the
rest operating asynchronously, with no control signals, all at rates up to
19,200 bps.
These configurations are set by adjusting the rotary switches and jumpers
located on the main board (see
Chapter 3
).
The unit implements asynchronous multiplexing using an over-sampling
technique. Each of the 12 channels is sampled at 76.8 kbps on the electrical
side while on the optical side the rate of sampling is doubled. Table 2-1 on the
next page summarizes the unit’s performance in its various configurations.
2.0 Introduction
Summary of Contents for MX880A
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