The UCP-GPIO uses contact closures to extend any Utah Scientific router control system to external devices. The unit provides 16 inbound contact closures (GPIs) and 16 outbound GPOs. These contacts can be configured for latching or momentary operation, and they are programmable for mapping the individual contacts to specific source-destination combinations.

In latching (revert) operation, the crosspoint associated with that contact is activated as long as the closure is active. When the closure is released, the router output is switched back to the input that was selected before the closure was activated. This mode of operation is generally referred to as “Joystick Override” mode.

The 16 outbound closures are provided by relays, allowing external devices such as tally lights or other indicators to be activated when a specific source-destination combination is active in the router.