Model 10BACI-422 Auxillary Computer Interface Card RS-422
is equivalent to a Model 10BACIA with an integral RS422 hardware interface on a 9-pin subminiature female socket (in place of the 10BACIA's standard RS232 interface).
The RS422 interface includes an extra pair of wires for communication of an external synchronizing pulse. This allows timed synchronous data collection, controlled by a master timing pulse. The 10BACI-422 is particularly useful in conjunction with the Model 10K488 Data Concentrator, since it allows the timing pulse generated by the 10K488 to synchronize the collection of data for all connected System 10 mainframes.
When an external synchronizing pulse signal is available through the RS422 interface—as it is when the 10BACI-422 is communicating with a Model 10K488 Data Concentrator—then you will need to enter a CLOCK (CLK) command and a MASTER TIMING CLOCK (MTC) command in order to "slave" the mainframe's scan cycle to this "master" pulse signal. The external sync pulses must be at a rate of 1 second ± 0.05%.