Linear Megacode Transmitter MDT-1A 100% new authentic Linear Part Compatible with all Linear access receivers and controllers and 318 MHz Megacode receivers. Includes: Transmitter, Visor Clip and Battery. The MDT-1A is a single-channel visor transmitter, designed for use with Linear's access control products. Megacode transmitters are permanently coded at the factory with one of over 1,000,000 codes, proving a unique code that is programmed to the receiver by learning the transmitter's unique digital code. The receiver is activated only from the memorized transmitters.