Thanks for that. I tried simply zipping up a .WAV file created by the program I mentioned and it compressed from 544kb down to 3.4kb. The original data file was 409 bytes, so although the result is 8 times bigger than the data file, storage is not too much of a problem. At this compression ratio (or rather expansion I suppose), a CD could store 80Mb of original computer data - more than was probably ever written for some of those computers!. paul -----Original Message----- From: ard(a)p850ug1.demon.co.uk [mailto:ard@p850ug1.demon.co.uk] Sent: 20 May 2003 00:26 To: cctalk(a)classiccmp.org Subject: Re: Preserving ancient media least Not at _all_ Just about every manufacturer did it his own way... I thought the common one was 'Kansas City', but that was not common on UK home computers (the BBC micro was perhaps the closest to it). No! Some did, many didn't. What's worse is that some manufacturers used a constant time for each bit (so that one state was a single cycle of 1200 Hz, the other was 2 cycles of 2400 Hz, say), but many other manufacturers used a single cycle at each frequency for the 2 states. This means the bit rate is not even constant... However, a reasonable quality digital audio recording of these old tapes might well be enough to preserver them (you could play it back to a real tape, or directly into the home computer). It's not an efficient way to store the data, but it's better than losing it totally. -tony