operating time

Short definition from Wiktionary

Noun

1. 1
   The time interval between the instant of the occurrence of a specified input condition to a system and the instant of completion of a specified operation.
2. 2
   The time interval between the instant a request for service is received from a user and the instant of final release of all facilities by the user or either of two users.
3. 3
   In conference calls, the time interval between the instant a request for service is received from one of a group of concurrent users and the instant all but one of the users have released all facilities.