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CHAPTER 2: Description
2.3 Connectors
Located on the rear of the Fallback Switch are three user data connectors
(“common,” “A,” and “B”) and one 8-pin modular jack for console control. The
user data connectors are DB25 female for RS-232 or RS-530, or M/34 female for
V.35.
The RS-232 Loopback Switch is identical to the RS-232 Fallback Switch, except
that it has an internal loopback plug instead of a “B” switch connector.
2.4 Switches and Indicators
A pushbutton is used to manually set the Fallback Switch to the desired position
(A or B). To prevent accidental switching, you must push the button and hold it
for several seconds for switching to take effect. An LED indicates the current
Fallback Switch position (regardless of whether you switch with the button or from
the console).
A pushbutton manually sets the Loopback Switch to the desired position (loop
or normal). To prevent accidental switching, you must push the button and hold it
for several seconds for switching to take effect. An LED lights when the Loopback
Switch has been set to loop back. The Loopback Switch will automatically switch to
normal upon power-up.
In both cases, five LEDs indicate lead status activity. For RS-232 switching, the
monitored leads are SD, RD, DCD, DTR, and RTS.
2.5 Alarming
The Fallback Switch supports console-controlled data circuit alarming on both the
“A” connector and the “B” connector (independent of switch position), while the
Loopback Switch supports alarming only on the “A” side. Each data line can be
programmed, through the console, to alarm on the following interface leads:
• SD, Send Data, present/absent
• RD, Receive Data, present/absent
• SCT, Serial Clock Transmit, present/absent
• SCR, Serial Clock Receive, present/absent
• RTS, Request to Send, high/low
• CTS, Clear to Send, high/low
