In telecommunications, the term lockout has the following meanings:
1. In telephone systems, treatment of a user's line or trunk that is in trouble, or in a permanent off-hook condition, by automatically disconnecting the line from the switching equipment.
2. In public telephone systems, a process that denies an attendant or other users the ability to reenter an established connection.
3. In a telephone circuit controlled by two voice-operated devices, the inability of one or both users to get through, either because of excessive local circuit noise or because of continuous speech from either or both users.
4. In mobile communications, an arrangement of control circuits whereby only one receiver can feed the system at a time. Synonym receiver lockout system. 5. An arrangement for restricting access to use of all, or part of, a computer system. Synonym protection.
Source: from Federal Standard 1037C and from MIL-STD-188
