13
CHAPTER 4: Configuration and Operation
The mux can accept and adapt to any data rate up to 14,400 bps on a
channel in this mode. To set a given channel for this mode, set that channel’s
STD switch position ON, all others OFF.
NOTE
Any time the mux’s STD switch position is ON (Mode 2, 3, or 5), the
signal input to the mux on Pin 14 will be retransmitted back out Pin 15.
This feature is not particularly useful for Mode 2 or 3, but for Mode 5 it
allows the mux to get the external clock on Pin 14 (Secondary Transmit
Data) and echo it on Pin 15 (Transmit Clock). This feature will also come
in handy if you ever need to do end-to-end testing (see
Section 5.3.1
).
4.2 Operating the Multiplexors
After connecting the multiplexors with the optical cable, connecting the
terminal devices to the individual channels (either directly or through the
adapter cables), and setting the channel configuration switches, connect both
multiplexors to their AC power sources. Note that the muxes have no AC
power switch. Each multiplexor is turned ON and OFF by plugging and
unplugging its power cord. Verify that the red POWER LED of each
multiplexor comes on when AC power is connected, and that the green
SDCD LEDs of both multiplexors come on when power is applied to the
second multiplexor.
Try transmitting through the multiplexors. If data does not seem to be
passing through, or if there seem to be errors in the data being transmitted,
see
Chapter 5
.
4.3 Interface Desription
This section describes the basic operating principles of the multiplexor and
the functions and characteristics of the channels’ electrical interface signals.
Instructions are also given on how to connect three asynchronous terminal
devices to a single channel of the multiplexor.
4.3.1 M
ETHOD OF
M
ULTIPLEXING AND
D
EMULTIPLEXING
Each channel of the multiplexor transmits three signals in each direction. All
signals in all channels are sampled simultaneously at a rate of 76.8 KHz. The
samples are then transmitted serially on the fiberoptic link and reconstructed
at the receiving end, where they are all simultaneously transferred in parallel
to the interface outputs.
