DEC VAXstation 3100 Owner's Manual page 149

lb exit terminal emulation mode, press |Ctfl/p| and press the
Return k^. T^e Model 30 s3rstem returns to local console mode —
(»>). ^
The Model 48 sjrstem (with the S3 switch in the up position) will
always attempt to use the serial line. The Model 38 system only
uses the information after you enter the DID command. The state
of the S3 switch is only read at power-up.
A-8 System Parameters