R2 Signaling is primarily used with E1 circuits. As shown in the table below, it contains more state information than standard E&M signaling:
|
SIGNAL |
FORWARD |
BACKWARD |
|
IDLE / ON HOOK |
ABCD = 1001 |
ABCD = 1001 |
|
SEIZE |
ABCD = 0001 |
ABCD = 1001 |
|
SEIZE ACKNOWLEDGE |
ABCD = 0001 |
ABCD = 1101 |
|
ANSWER |
ABCD = 0001 |
ABCD = 0101 |
|
CLEAR BACKWARD |
ABCD = 0001 |
ABCD = 1101 |
|
CLEAR FORWARD |
ABCD = 1001 |
ABCD = 0101 |
|
BLOCKED |
ABCD = 1001 |
ABCD = 1101 |
When connected to POTS lines to the FXO cards in the system, the ANSWER state can be generated by either the Timer or VAD-based Answer Supervision. The CLEAR state (forward or backward) is generated by the Tone-based Disconnect Supervision.
When connected to DID (reverse battery) trunks, all of the signaling is controlled via the battery state on the trunk circuit.
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