2N Analogue GSM gateway 2N EasyGate PRO - Manual, 1749 v1.03 - Manual (Page 22)

SMS Sending Input Connection 2.5
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2.5 SMS Sending Input Connection
You have got a special connector for easy connection to EasyGate. The connector is
equipped with screwing clamps to connect wires leading to a switching contact (device
to be monitored). The other connector end can be connected to the respective
EasyGate panel connector.
The input is designed for the switching contact connected between the input pins. The
input is activated by contact closing (pin interconnection).
A transistor switch or logic signal can be used too. The pin near the telephone line
connector is connected to GND of the device the second one is active. Please, respect
the loop current polarity. The input is over-voltage protected (up to +12V DC).