The Care and Feeding of ISDN4BSD
6.1.4 Idletime Calculation for	6.1 The isdnd.rc Configuration	6.1.6 Configuring Fixed Unit-Length

6.1.5 Configuring Simple Mode for Outgoing Calls

For simple mode, the selected unitlength must be 0 (zero) and idletime-outgoing greater than zero.

The outgoing traffic is constantly monitored, and in case there was no traffic taking place for the time in seconds specified by idletime-outgoing the call is closed.

Typical idletime-outgoing values in simple mode are 10 to 30 seconds.