Hi ogiebendogie,
Depending on the release and type of processor, yes. If you have a current ACS processor, program a night button on ext 10 (#503, 3 & pick your button). Then set the day delay (#506, 1) to 5 or six rings. That's for day attendant backup. Set the night delay for two rings (#506, 2) for caller ID or immediate (0 rings) if you don't need caller ID. The reception phone will ring until answered by the attendant. On the newer ACS units, you set the delay for each line independant of the others (01, 02, 03 ...)
If you don't have the number of rings your choices will be 1, immediate or 2, delayed (three rings). You can set the schedule for night only (#507, 3).
Keep in mind that a caller will hear one more ring than the system is set to. So, delayed answer for five rings, your caller hears six.
-Chris