Sentry 1 channel transmitter Code Hopping short range frequency @433.92 MHz, range up to 100 metres in clear line of sight. The SENTRY Code Hopping transmitters are secure products utilizing KEELOQ encryption, operating in the 433MHz range. These are standard encrypted remote controls that generate unique encrypted transmissions with each keypress. Employing secure KEELOQ encryption, they provide the ultimate level of security- they are exceptionally resistant to code grabbing. Each transmitter is unique and contains a unique serial number that is never duplicated. KEELOQ is a trademark of Microchip Technology Inc.