A switch command initiates one external request for evaluation (read-write). (1) Clear - Clears all switch commands on the channel. (2) Lockout Of Protection - Prevents any of the working channels from switching to the protection line by issuing a Lockout of Protection request [unless a request of equal priority (i.e., a Lockout of Protection) is already in effect]. (3) Forced Switch of Working (to Protection) - Switches the working channel to the protection line unless a request of equal or higher priority is in effect, by issuing a Forced Switch request. (4) Forced Switch of Protection (to Working) - Switches the working channel back from the protection line to the working line unless a request of equal or higher priority is in effect, by issuing a Forced Switch request. This command applies only in the 1+1 architecture. (5) Manual Switch of Working (to Protection) - Switches the working channel to the protection line unless a request of equal or higher priority is in effect, by issuing a Manual Switch request. (6) Manual Switch of Protection (to Working) - Switches the working channel back from the protection line to the working line unless a request of equal or higher priority is in effect, by issuing a Manual Switch request. This command applies only in the 1+1 architecture for the null. (7) Exercise - Exercises the protocol for a protection switch unless a request of equal or higher priority is in effect, by issuing an Exercise request and checking the response on the APS channel. Reading this variable always returns zero (0).