Modular Digital Multitrack (MDM)   

Modular Digital Multitrack systems provide basic multitrack modules in the form of eight-track recorder/players and controller units which can be combined to create a greater number of available tracks. 
At present two formats are widely used.
Alesis/Fostex Adat
The Adat system allows recording and playback of eight tracks of digital audio per machine using high quality S-VHS video cassettes. 
Tascam DA-88
The DA-88 system provides the same modular features as the Adat system but differs in its use of Video-8 cassettes as storage media.