Editing Programme Delivery Control (section)

==PDC Packets==
PDC is transmitted once a second in special packets addressed as magazine 8 and text row 30. Since this row is not displayable it does not interfere with normal pages. Packet 8/30 has various formats specified by ETSI and PDC is format 2. Each packet 8/30 format 2 also has a label number and there can be up to four labels transmitted at a time. Each label contains the scheduled start time and date for a programme and flags to indicate the state. Each programme is assigned a label and in general a label will follow this sequence.
* PRF Set – Prepare for Record. This will tell a VCR to wake up and get ready. This happens about 40 seconds before the programme is active.
* PRF Clear – The VCR should be recording.
* RTI – Record Terminate/Interrupt – Tells the VCR to stop recording. This label is held for 30 seconds after the programme ends.

There are complicated rules for the case where a programme is interrupted by another one as in the case of a film with a break for news in the middle.

There is also a TIMER flag that indicates that there is no valid PDC and that the VCR should use its own timer.