The Linear Model ACT-21A 1-Channel Key Ring Transmitter is designed for use with Linear’s garage door opener line. The Lineaer ACT-21A is a single-channel device supplied with a quick-disconnect key ring. Also included are lithium batteries with a five-year service life. A unique 10-second time-out feature prevents the system from being shut down by a single transmitter transmitting continuously.

The transmitter is MegaCode format, which means each transmitter is factory preprogrammed with one of over 1,000,000 codes, virtually eliminating the possibility of code duplication. Because the receiver “learns” each specific code, no unauthorized person can gain access to the system by reprogramming a transmitter.

Product Features:
-Compatible with all Linear access receivers and controllers 
-Supplied with quick-disconnect key ring 
-Factory programmed MegaCode format supports over 1,000,000 codes 
-Two type 1616 lithium batteries supplied 
-RF frequency: 318 MHz 
-Dimensions: 1.25″ W x 2.25″ H x 0.5″ D