Broadcast industry term for communications circuits (as distinct from Programme circuits).
Originally just the communications path from the control room or gallery, in particular from the director, to the operational crew on the studio floor, i.e Talking Back to the studio.
Now used as a generic term in the broadcast industry for almost any form of operational communications with, or between, crew and/or presenters.
Production Talkback normally carries just the voices of the director and production assistant to all operational personnel involved in a production. Dedicated circuits for specific departments such as sound and lighting will usually comprise Production Talkback overlayed with the departments own communications and are known e.g. as Sound Talkback and Lighting Talkback, etc.
Communication from the 'floor' back to the control rooms other than via the programme circuits is known as 'Reverse Talkback'.
American term now adopted more widely. Stands for 'Interrupted Fold Back'. Usually a feed of cue programme which can be keyed over or 'interrupted', usually by the director, in order to speak to a particular person or people; most commonly to a presenter.