The Model D-22D 2-Channel, 2-Button Lockout Transmitter is a two-channel transmitter that can initiate two separate functions. This transmitter is used in remote switching applications where a portable two-channel transmitter with 2-button lockout is required. Pressing either button will activate channel one. For security, both buttons must be pressed at the same time to activate channel two. Each transmission causes the red LED indicator on the front of the transmitter to light, showing that the transmitter is sending a signal and that the battery is in good condition.