These ports are found on the rear of all IP Office control units. They are used for connection to external switching relays. The port uses a standard 3.5mm stereo jack plug for connection.

The IP Office is able to open (high resistance), close (low resistance) or pulse (close for 5 seconds and then open) two switches within the port. Either switch can be operated separately. These switches are intended for activation of external relays in systems such as door opening systems.

In installations where this port is connected to a device external to the building, connection must be via a MDS2 Surge Protector and a protective ground connection must be provided on the IP Office control unit. When using the MDS2 on the Ext O/P port, use only the Line 1 and Equipment 1 jacks, do not use the Line 2 or Equipment 2 jacks.




ext op port


Switch 1.


Switch 2.


0 Volts (Ground/Chassis)

Switching Capacity: 0.7A.

Maximum Voltage: 55V d.c.

On state resistance: 0.7 ohms.

Short circuit current: 1A.

Reverse circuit current capacity: 1.4A.

Ensure that pins 1 and 2 are always at a positive voltage with respect to pin 3.


3.5mm stereo audio jack plugs are frequently sold as pre-wired sealed modules. It may be necessary to use a multi-meter to determine the wiring connections from an available plug. Typically 3 (common to both relays) is the cable screen.