 Scanners were Line Scanners (LSC), Universal Trunk Scanners (USC), Junctor Scanners (JSC) and Master Scanners (MS).The first three only scanned for supervision, while Master Scanners did all other scan jobs.For example, a DTMF Receiver, mounted in a Miscellaneous Trunk frame, had eight demand scan points, one for each frequency, and two supervisory scan points, one to signal the presence of a valid DTMF combination so the software knew when to look at the frequency scan points, and the other to supervise the loop.