Kramer Electronics VS-4228 - Manual (Page 11)

8 VS-4228 - Overview
Some older broadcast equipment contains 3 RS-422 connectors; RS-422-In, RS-
422-Out and RS-422-In/Out. You can only connect a master to a RS-422-In port
and you can only connect a RS-422-Out port to a slave. When connecting to a RS-
422-In/Out port the unit changes dynamically, automatically reconfiguring the 9-pin
D-sub port pins to be either a master or a slave.
3.2.6 More Than One Slave
Communication between one master and one slave is simple. However,
communication between one master and several slaves, for example, in
duplication applications, is more complicated.
If all the slaves were to respond simultaneously to a master command, the system
would lock up. To avoid such a situation, a special algorithm in the VS-4228
dictates that the master receives only the response from the highest priority slave
(the lowest numbered slave device) with more than one slave device. For
example, in a setup in which port # 7 is the master, and ports # 5, # 3 and # 6 are
slaves, the VS-4228 only transmits to the master the reply from port # 3 and
discards all the other replies.
Pay special attention: in broadcast applications, the most common reply message
from a slave is the TIMECODE data, therefore, with the above-described
algorithm; the response comes from the lowest numbered slave.