Also spelled as "pass thru".
1. Noun. A signal or power output that is the same as the input. Many ML PD s and touring dimmer rack s have provision for the power to pass through via the Cam-Lok connectors. Almost all moving lights and other DMX512 receiving devices have a DMX Out or DMX Thru allowing the user to daisy chain. Be aware that on MIDI devices, there is a distinct difference between MIDI Out and MIDI Thru. MIDI Thru is the same as MIDI In; MIDI Out is affected/altered by the device.
2. Noun. An approved hole or chase via which temporary cables can be run. See mouse hole.