Burst Electronics AS4x1 - Manual (Page 6)

4 AS4x1 Audio Switch
Remote Control
The RS232 Commands apply to the Model AS4x1R only.
The data transmission to the AS4x1R is 2400 baud 8N1.
To cause the AS4x1R to switch to an input, issue the
command: Ax, where x is the channel number. Example:
A2 will cause the AS4x1R to switch to channel two.
If a VS4x1R Video Switcher and a AS4x1R Audio Switcher
are used together, then the command Bx will cause both
units to switch.
Commands to the AS4x1R:
Command Function
Ax Switches to x Channel
Bx Switches to x Channel
and causes the VS4x1 to also switch