Tally, Talkback and Genlock: Gallery Terms in Plain Words

Why the vocabulary matters before the wiring

Most of the misunderstandings I hear in galleries come from words used loosely. A producer asks for tally and means the red light on the camera; an engineer hears a request for a signal path that the mixer has to generate. Both are right, and neither gets what they wanted. When a studio is planned as one system, every person involved needs the same short list of terms, and needs to know which part of the equipment each one belongs to.

This note takes three of them: tally, talkback and genlock. They sit at different points in a gallery, yet they fail in a similar way. When one is poorly understood, the fault usually shows up on air, at the worst moment, and it is blamed on whichever device happens to be nearest.

Tally: a signal, not just a lamp

A tally is a message from the vision mixer saying which source is currently on air and which is selected next. The red lamp on top of a camera is only the visible end of it. The same message can light a name on a multiviewer tile, change a border colour on a monitor, or warn a presenter that the camera facing them is live.

The practical point is that tally travels as its own signal, separate from the picture. It has to be routed from the mixer to every place that needs it, and each destination has to be told what the mixer's output actually means. If a camera is mixed into a graphic, or a router sits between mixer and monitor, someone has to decide whether that still counts as on air. That decision is made during planning, not discovered during rehearsal.

• Red usually means on air, green or amber means next
• Tally follows the mixer's logic, not the camera's
• Check it on every monitor, not only on the cameras

Talkback: the private conversation of the gallery

Talkback is the intercom system that lets the director, vision mixer, sound supervisor and camera operators speak to each other while the programme runs. It is deliberately kept apart from programme sound, because what the crew says must never reach the viewer. That separation is its whole purpose, and it is where careless wiring does the most damage.

A well-built talkback system has several channels, so the director can speak to the floor without interrupting the sound desk. Someone also has to decide who can hear whom, and who can break into which line. A clear structure of channels, written down and labelled at each panel, saves more rehearsal time than any piece of equipment, and it is the first thing a new operator should be shown.

Genlock: keeping every picture on the same beat

Genlock means locking every video device to one shared timing reference, so that all pictures start each frame at the same instant. Without it, a mixer switching between two cameras has to reconcile two slightly different clocks, and the result can be a brief roll, a flash or a jump at the cut.

In a gallery, one reference generator feeds a distribution of timing signals to cameras, mixer, routers and converters. The common fault is not the absence of a reference but a device quietly running on its own clock, because a cable was moved or a setting was never saved. If switching looks unsteady, I look at the timing chain first, before suspecting the cameras or the mixer.

• One reference source for the whole gallery
• Label every timing cable at both ends
• Confirm each device reports it is locked

How the three terms depend on each other

Tally, talkback and genlock look like separate topics, yet in one gallery they share the same cable routes, the same patch bays and often the same engineer's attention. A change made for one can disturb another. Moving a router input, for example, may alter which tally is delivered to a monitor and, if a device is replaced, which timing signal it receives.

This is why we treat integration as the planning of relationships rather than a list of products. Each connection is drawn, named and tested against the other two. A short written map of where each signal starts, where it ends and what is meant by its name gives a technical lead something to hand to a new colleague, and gives the producer a way to ask for changes precisely.

A short test routine for these autumn weeks

As studios return to longer schedules, a quick check before the first rehearsal is worth more than a long one after a fault. Walk the gallery with someone at the mixer and someone on the floor. Select each source in turn and confirm that the tally shows in every place it should, from camera lamp to multiviewer tile.

Then call each talkback channel from each position and listen for crosstalk. Finally, look at the timing reference and confirm that every device reports it is locked. The whole routine takes well under an hour in a studio of ordinary size. Write the result down, keep the page near the desk, and repeat it whenever equipment is moved or replaced.

• Cycle every source and watch every tally
• Call each channel from each position
• Confirm timing lock on each device