Westermo MRD-3x0 - Manual (Page 48)

48 6623-3201
For example if the guard time is set to 2 seconds and the dis-
connect character is 3F (? ASCII) then the disconnect sequence
would be:
<2 seconds>???<2 seconds>
Upon receiving this sequence the MRD-3xx would disconnect
from the currently connected serial port and return control
to the virtual terminal.
Figure 42: Circuit Switched Data (CSD) mode port multiplexed page.