PDC

PDC stands for Primary Domain Controller. There can be only one PDC in a domain. The PDC holds the main SAM database and provides the main logon authentication for the network. The PDC must be the first server installed on a network. Almost all of the admin work for a network is done at the PDC console.

The PDC feeds the SAM database to the Backup Domain Controllers (BDCs) every five minutes. If the PDC were to crash, a BDC would be able to take over the network until the PDC was fixed and rebooted.

Servers cannot join a new domain without first reinstalling Windows NT.

PDC also stands for Programme Delivery Control, a feature found in most modern VCRs in Europe.

A signal is transmitted in the VBI (along with things like Teletext) which ensures that if a progamme is running late, then it will be recorded in its entirety.

an example: you want to record The Simpsons, but the tennis that's on before it is so exciting that it over-runs by a few minutes. Without PDC, you'd get a few minutes of tennis, and miss the end of Spingfield's finest. With PDC, however, the VCR knows when the programme really starts, and really finishes.

All you need is a compatiable VCR, a decent signal from your aerial (it also works with some satellite channels), and when programming the timer, make sure you set the start time to exactly as it is in the listings, or use a VideoPlus code.

When it comes to a little before the time to start recording, your VCR will take a look at the appropriate channel, and look for a Programme Identifier Label - a code which has the channel and original start time in it. This is transmitted every second while the programme is on, and stops once the show has finished. So no matter what time the VCR thinks it's going to stop recording at, it'll stop when the broadcaster stops transmitting the PIL for that programme, be it early or late.

The PDC specification also allows for remotely pausing the tape, and then starting again later - technically, broadcasters could miss out adverts when you're taping a show. But they don't, do they?

Some VCRs also support the PTY code. This allows a code to be allocated to a strand of progammes, eg all comedy. Scottish TV have one code for daily showings of Coronation Street, and Channel 4 use a code for Brookside and another for Channel 4 News.

Unfortunatley, PDC isn't available everywhere in the UK - some broadcasters, notably ITV regions haven't implemented it yet. However, if you're buying a new VCR, make sure it does have PDC. You'll wonder how you did without it.

much more info: http://625.uk.com/pdc/ and http://www.bbc.co.uk/reception/tv_pdc.shtml