The Linear ACT-34B 4-Channel Key Chain Transmitter (ACP00872) is a compact, secure remote designed for use with Linear access control systems. Featuring MegaCode format, it provides over 1,000,000 unique codes to prevent duplication and ensure robust security. The transmitter includes a quick-disconnect key ring for convenient carrying and operates on two 3V lithium batteries with a 5-year service life. It is compatible with a wide range of Linear access controllers and receivers, including the AE1000Plus and MDR-2, and features a 10-second time-out to prevent continuous signal transmission.