2N Analogue UMTS gateway 2N SmartGate UMTS - Manual, 1699 v1.1.0 - 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 SmartGate UMTS. The
connector is equipped with screwing clamps to connect wires from a switching contact
(device to be monitored). The other connector end can be connected to the respective
2N® SmartGate UMTS panel connector.
The input is designed for the contact of relay 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. There is over-voltage protection up to +12V DC there.