Visonic MCT-104(868) 4-button handheld Powercode UHF transmitters for supervision of alarm and remote control systems 868 MHz, maximum Tx Power: 14 dBm @ 868 MHz, encoding: 24-bit digital word - over 16 million combinations, transmission duration: As long as the button is kept pressed or 3-seconds (depending on DIP switch setting), power Source: 3.6 V battery size 1/2 AA Tadiran type TL-2150 or equivalent