The TB4 is a one space rack mount unit designed to be the control room module and the communication module all in one. There are four balanced stereo inputs and two balanced alternate speaker outputs on XLR connectors. These signal paths are completely passive. No active electronics (i.e. op amps), no relays, no fet switching or VCA's to color the audio signal path. A four ganged gold plated stepped attenuator, that tracks to .05db, is used for level control.

There is a completely seperate stereo cue mix input and output with a master level control on TRS 1/4\" jacks.

The talkback has a remote microphone with a 12 foot cord so it can be placed near the engineer or producer. The talkback switch silently activates the talkback without any clicks or pops in the headphones, dims the control signal and the talkback level controls amount of signal going to cue mix.

The engineers headphone, mounted on the front panel, selects either the control room signal or the cue mix. It also has a separate output and level control.