Where can I find DTMF test data?

This question often comes up, because people still need to develop DTMF applications, and yet the two key sources of well accepted test data have largely lost interest in supplying it. Those sources are Mitel (now Zarlink Semiconductors), and Bellcore (now Telcordia).

The old Mitel CM7291 DTMF test tape is no longer available. However, it appears that if you send an e-mail to Zarlink semiconductors, they will happily send you a pair of MP3 files of the two sides of the old tape. I don't think they charge for this. It should be noted that they seem to have set the recording level too high, and there is some clipping in these files. However, overall the results from testing with these files seem comparable to the results with the old cassette tapes.

The Bellcore set of three talk-off test cassettes was available from Telcordia, for about $200, until about the year 2000. When they ran out of their last batch of cassettes, they stopped supplying them. A set of 16 bit 8000 sample/second wave files, carefully digitised from one of the last sets of tapes to be sold, is used for testing spandsp. "Carefully" means a good quality cassette machine was used. with it's speed tweaked to get the check tone dead on the right frequency; record levels were chosen with care; a good quality sound card was used; and the cabling was checked to minimise hum. These files are a legitimate copy of purchased tapes. The material is copyright, though, and these files cannot be freely distributed.

Since the Bellcore material can no longer be purchased, a few people wrote to Telcordia to ask if they could have a copy of the files used for the spandsp work. Someone at Telcordia agreed a few times, and the files were supplied to these people against consent e-mails from Telcordia staff. However, some time ago Telcordia stopped giving this consent, and said they were going to make the material available on CD for about $2000. Telcordia should be consulted for the actual availability of these CDs.