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|