Linear act-21 keychain remote Features and Specifications Linear Moore-o-Matic Megacode format 1-button mini ""key chain"" size (2"" by 1"") transmitter for gate or garage door openers Smart coding system, no dip switches, 318 Mhz frequency 3V lithium ""button cell"" batteries and a key ring included The batteries should last up to five years with normal use Compatible with ALL Linear Megacode System products