Operation; Manual Switching; Dry Contact Closure Switching; Serial Rs232 Switching - Black Box 12 VDC load User Manual

5. Operation

When power is applied to the A/B Switch, one of the LED switch position indicators (A or B) on the front of the
unit will illuminate to show the connection state of the switch. Indicator A lights when the switch is in position A,
and Indicator B lights when the switch is in position B. If neither or both LEDs are lit, then a fault has occurred, or
power has been removed.

5.1 Manual Switching

All A/B Switch models can be manually switched using the push button switches located on the front of the unit. To
select the connection state, the appropriate push button switch must be held for one second before the unit will
switch. This is to minimize the risk of inadvertently switching the A/B Switch.

5.2 Dry Contact Closure Switching

You can also switch connection states and monitor the status of the A/B Switch using the remote control
connections on the six position terminal block, located on the rear of the unit. Connecting (shorting) input A (pin 1)
to Ground (pin 2) for a minimum of approximately 100 msec will cause the unit to switch to the A position, and
connecting (shorting) input B (pin 3) to Ground (pin 2) for a minimum of approximately 100 msec will cause the
unit to switch to the B position. If desired, the A or B control input can remain connected to the Ground input,
which will disable all other control interfaces including the front panel pushbutton switches from being able to
switch connection states of the A/B Switch. Note that to insure reliable operation, the external dry contacts and any
associated cable connected to the 6 position terminal block should not exceed 100 ohms resistance. Once the A/B
Switch has switched connection states, the status relay contact pin 5 will be internally connected (shorted) to either
pin 4 (switch in position A) or pin 6 (switch in position B). See table 5.1 for the pin assignments on the 6 position
terminal block.
Pin 1
Pin 2
Pin 3
Pin 4
Pin 5
Pin 6

5.3 Serial RS232 Switching

A/B Switch models that support serial remote control can be switched using commands over a serial RS232
communications line. The parameters of the A/B Switch console port are fixed at 9600 baud, no parity, 8 data bits,
and 1 stop bit (commonly abbreviated as 9600, 8, N, 1). To communicate with the A/B Switch you will need a
serial terminal or similar device configured to these settings. Use a straight thru M/F cable to connect the A/B
Switch console connector to this terminal or other device that follows the standard IBM PC DB9 serial port pinout.
See table 6.1 for the A/B Switch console port connector pin assignments.
When the A/B Switch powers up, it will send a sign-on message followed by a prompt character ">" to your serial
terminal device. After each command and the associated response, the A/B Switch will again issue a prompt
character. For systems where the console port is being commanded by software, the software should wait for this
prompt character before sending each and every command to the A/B Switch. All commands are case insensitive
A/B SWITCH WITH REMOTE INTERFACE
(connected to pin 5 = A)
(connected to pin 5 = B)
Table 5.1 Six position terminal block pin assignments
A control input
Ground
B control input
Status Relay A contact
Status Relay COMMON
Status Relay B contact
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