Linear Access Mini Digital Single Button Transmitters w/MegaCode (ACT-31B):
The ACT-31B is a single button miniature transmitter. Linear's MegaCode series of digital transmitters are wireless radio controls designed for use with MegaCode format receivers. The MegaCode radio format provides unparalleled security. Each transmitter is preset at the factory to one of over 1,000,000 codes.