A VTR standard using 1/2” tape cassettes for recording digitised composite (coded) PAL or NTSC signals sampled at 8 bits.
Cassettes are available for 50 to 245 minutes.
Since this uses a composite signal the characteristics are generally as for D2 except that the 1/2” cassette size has allowed a full family of VTR equipment to be realised in one format, including a camcorder.
References
Pank, B., Editor, 1994, The Digital Fact Book, 7th Ed, Quantel, Newbury, UK