20 All services
21 All asynchronous services
22 All synchronous services
23 3.1kHz services
24 Synchronous point-to-point connections including PAD's (all synchronous data services)
25 Asynchronous point-to-point connections including PAD's (all asynchronous data services)
26 Data packet sending including PAD's (all synchronous data packet services)
27 Services with PAD-share
29 Digital connection with 12kbps