RETURN Voice Networking


Trunk Signaling Schemes

It is necessary to understand the signaling that occurs on trunk circuits. Signaling states include ON-HOOK and OFF-HOOK supervision, Disconnect supervision, dialing supervision (Pulse Dial/Tone Dial), and Start Dial supervision.

Most signaling schemes use DC currents to represent signaling states, but analog (AC) systems also exist that use tones to represent specific states.

The following subsections discuss the types of signaling:

Loop Start 2-Wire Loop Start Trunk Signaling
Ground Start 2-Wire Ground Start Trunk Signaling
Single Frequency SF Signaling (AC Signaling)
E&M Signaling E and M Signaling
Start Dial Start Dial Supervision