This is the duration, from 1 to 300 seconds (default 60), that a bypass relay stays active on a POTS splitter line before automatically returning to normal operation as a fail-safe. Admins set this so that a technician using the bypass relay for line testing doesn't have to remember to reset it manually, since the same timer value applies to every port. For example, an admin might lower this to 30 seconds when running quick loopback tests so relays don't stay bypassed longer than needed.