VEGA Phoenix PSI Data Fax Modem - Manual (Page 115)

AT Commands
692302 6-27
S93 to S103 Reserved
S104 Maximum Connection Time
This register controls the maximum connection time in minutes. Regardless of the
data traffic, the modem automatically disconnects when the maximum time has
elapsed. The values for this register are between 0 and 255 in 1-minute intervals.
Default: 0
(I.e., the timer function is disabled.)