D4 (SF) Framing Format
| Ringing |
| 0 | 0 |
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LCF | LO (on hook) | 0 | 1 | 0 | 1 | |
signaling (FXO- |
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FXS) |
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| LCFO | LC (off hook) | 1 | 1 | 1 | 1 |
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| Ringing | RG (service | 0 | 0 | 0 | 0 |
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LCF | LO (on hook) | 0 | 1 | 0 | 1 | |
signaling with |
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RLCF |
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| RLCF | LC (off hook) | 0 | 1/0 | 1 | 1 |
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| LCFO | RG (service | 1 | 1 | 0 | 0 |
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| Ringing |
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LO | LCF | 0 | 0 | 0 | 0 | |
battery signaling |
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(DID) |
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| LC | RLCF | 1 | 1 | 1 | 1 |
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LCF (on | LO (on hook) | 0 | 0 | 0 | 0 | |
reverse battery | hook) |
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(enhanced 911 |
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apps) |
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| RLCF (off | LC (off hook) | 1 | 1 | 1 | 1 |
| hook) |
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E&M signaling | on hook | on hook | 0 | 0 | 0 | 0 |
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| off hook | off hook | 1 | 1 | 1 | 1 |
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Subscriber- | LO | LCF | 0 | 1 | 0 | 1 |
provided |
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supervision (FXS- |
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FXO) |
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| LC | Ringing | 1 | 1 | 0 | 0 |
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