Table 4: Ground-Start Signaling at FXO Interface for Call Initiated by the FXO Interface (continued)
Signaling Bits from FXOSignaling Bits to FXO
0111FXO goes off-hook (closes loop)
0111Duration of call
Table 5: Ground-Start Signaling at FXO Interface for Call Initiated by the FXS Interface
Signaling Bits from FXOSignaling Bits to FXO
11 (A=1, B=1)01 (A=0, B=1)Idle (before call starts)
00/01 (B-bit toggles)01FXS goes off-hook (grounds tip and
sends AC ring signal)
0111FXO goes off-hook (closes loop)
0111Duration of call
Table 6: Ground-Start Signaling at FXS Interface for Call Initiated by the FXS Interface
Signaling Bits from FXSSignaling Bits to FXS
01 (A=0, B=1)11 (A=1, B=1)Idle (before call starts)
0100/01 (B-bit toggles)FXS goes off-hook (grounds tip and
sends AC ring signal)
1101FXO goes off-hook (closes loop)
1101Duration of call
Table 7: Ground-Start Signaling at FXS Interface for Call Initiated by the FXO Interface
Signaling Bits from FXSSignaling Bits to FXS
01 (A=0, B=1)11 (A=1, B=1)Idle (before call starts)
0011FXO grounds ring
0001FXS goes off-hook (grounds tip and
sends AC ring signal)
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