8
PBX Loop Start Trunk Port
In this configuration, the unit supplies a 24V talk battery and loop current detection.When the unit detects a loop
resistance between Tip and Ring, it activates.When the loop opens, the page ends.The unit follows the status of the
trunk port.
Before configuring the UTI3
1
2 for a loop start trunk port, make sure that the power is disconnected and all other
connections are completed. Move the slide switches on the UTI3
1
2 to the positions shown below. Use a modular
telephone cord to connect the unit to the phone system.
The center two conductors are Tip and Ring (24V DC) and have a specific polarity as shown in the figure below. If
the polarity that the trunk requires is opposite, you can use a reversing modular cord to make the connection or
reverse the connection through a modular block.The Trunk Disconnect feature is available in this mode (
description
on page 9
).
PBX Ground Start Trunk Port
In this configuration, the unit supplies 24V talk battery, a contact in the Tip circuit, and loop current detector in the
ring circuit.When the ground start trunk grounds Ring, the unit responds by closing the connection to Tip, which
completes the access procedure.When the loop is opened, the page ends.The unit follows the status of the trunk.
Before proceeding, make sure that the power is disconnected and all other connections are completed. Move the
slide switches on the UTI3
1
2 to the positions shown below. Use a modular telephone cord to connect the unit to
the phone system. Connect the GND STRT terminal on the UTI3
1
2 to the PBX ground. This is typically the AC
ground for the PBX system. If the PBX is using the same Earth Ground as the UTI3
1
2, the Earth Ground terminal
can be shorted to the GND STRT terminal instead of running a ground wire from the PBX.
The center two conductors are Tip and Ring (24V DC) and have a specific polarity as shown in the figure below. If
the polarity that the trunk requires is opposite, you can use a reversing modular cord to make the connection or
reverse the connection through a modular block.The Trunk Disconnect feature is available in this mode (
description
on page 9
).
IMPORTANT -
When the GND STRT terminal is connected to Earth Ground, it is important that none of
the UTI3
1
2 system ground terminals are connected to Earth Ground. These terminals may accidentally be
connected to Earth Ground when external equipment, such as a CD player, tuner, announcement device, etc.,
is connected to the UTI3
1
2.The UTI3
1
2 ground points are: the closure return terminal for the Trunk/Page
Port jack, the contact closure (GND) and the left-most Dry Audio input terminal of the Override jack, the
C terminal for the Night Ring, and the Tone Trigger input.The background music input and page outputs are
transformer-isolated and are unaffected by Earth Ground. If the UTI3
1
2 system ground is tied to Earth
Ground, then the UTI3
1
2 talk battery voltage will be shorted to ground and the unit will not function
properly. For location of UTI3
1
2 system ground terminals, refer to the
UTI3
1
2 Block Diagram
.
