This GSM door opener with a remote on/off switch for authorized calls for free calls, which can be operated from anywhere without distance restrictions. Features: 1. 850/900/1800/1900MHz quad band, can be used in the global GSM network. 2. No call charges. The GSM relay switch answers the call from the authorized number and then performs an on/off operation on the first "ringing". 3. Security - Use the caller ID to identify and ignore unknown callers. 4. Add or remove users with the SMS Text command. 5. There is no need to provide remote controls or buttons for different users. 6. Up to 200 authorized phone numbers can be configured at the specified time. 7. The relay operation will return a text message confirmation to the owner or authorized call, which can be edited by the user. 8. The relay closing or opening time is programmable. 9. With metal casing, IP30 protection level. The metal casing and system are safely isolated, especially suitable for industrial control applications. 10. Small size and support for wall mounting. 11. Multiple applications. Specification: Model: RTU5024 GSM frequency: 850/900/1800 / 1900MHz Network type: 2G Support: 2G, 3G, 4G Digital output: NC / NO dry contact, 3A / 240VAC DC power supply: 9-24VDC / 2A SIM card: standard SIM card Antenna: 50Ω SMA antenna interface Temperature range: -20~ + 60°C Humidity range: relative humidity 90% Package Size: about 13 x 9.5 x 3cm/5.12 x 3.74 x 1.18in Package List: 1 x GSM Mobile Phone Access Controller 1 x Antenna 2 x Terminal 1 x English Manual . Note: Please note that the new type and old type of this product will be sent randomly, and make sure you will not mind before ordering.