This specifies the minimum duration that the gateway will wait, after going from OFF-HOOK to ON-HOOK, before setting a channel available for new calls. If this delay is too short and that we were request an outbound call just after going ON-HOOK, the ON-HOOK OFF_HOOK transition can be seen as a simple hook flash by the switch instead off the end off an old call and a new call begining. According to R11-34 of the BellCore GR506 spec: R11-34[442] To produce a flash signal, an SPCS outgoing interface shall produce a momentary on-hook signal with a duration between 400 and 800 milliseconds. So the recomended default value for this parameter is 2000 milliseconds, in order to be sure that going ON-HOOK and then OFF_HOOK won't be seen as a simple hook flash.