Presfax

History

Presfax was a system used within the BBC to communicate junction timing information, mainly from London to regional/national playout centres elsewhere in the UK.

With the advent of regional opt-outs from the main ("network") BBC1 and 2 programmes, it was important that playout directors knew exactly what programmes and trails were going to be played out next, almost to frame accuracy.

This allowed regional programmes and trails to be seamlessly switched in for the regional viewers.

The name is derived from "Presentation Facts" - although it's likely the 'fax' bit is simply a nod to Ceefax.

Technical Explanation

The BBC's network feeds arrived in regional studios as PAL video circuits, typically containing teletext, ITS and Sound in Syncs. Therefore, Presfax could be inserted into the teletext service as databroadcast packets to avoid the need for any additional data circuits.

The display itself was based on a standard Level 1 teletext page, having 25 rows by 40 columns.

The system we're most familiar with was written by Peter Kwan of MRG systems. It used MRG's AV350 box to encode, decode and display Presfax packets - as well as PDC - for both BBC1 and BBC2.

The AV350 could receive schedule information via a serial interface from either of two automation systems.