KKMoon RTU5024 GSM gate opener relay switch control has on / off switch by authorized phone free calls, 850 / 900 / 1800 / 1900 MHz quad bands, no call charges required, GSM relay switch answers the call from authorized number then carries out the turn on / off action, secured caller-ID for identification and unknown callers are rejected, add or remove users by SMS text command, up to 200 authorized phone numbers can be configured, relay action will return a SMS confirmation to the owner or authorized call and this function is editable by user, programmable relay close or open time.