Signaling is not both way. In Xymphony, either Incoming calls disabled or Outgoing calls disabled should be check marked in Common Properties page of the relevant channel.
Idle state bits of C and D should be set as 0 and 1 respectively.
ZSL/SL Signalling bit states
| Tx | Rx | Direction | Signal | Tx | Rx |
| A B | A B | | | A B | A B |
| 1 1 | 0 1 | <-> | Idle | 0 1 | 1 1 |
| 1 0 | 0 1 | -> | Seizure | 0 1 | 1 0 |
| 1 0 | 1 1 | <- | Seizure Ack | 1 1 | 1 0 |
| 1 0 | 1 0 | <- | ANI Request | 1 0 | 1 0 |
| 1 0 | 1 1 | <- | ANI Request End | 1 1 | 1 0 |
| 0/1 0 | 1 1 | -> | Decadic Dialing | 1 1 | 0/1 0 |
| 1 1 | x x | -> | Clear Forward | x x | 1 1 |
| 1 0 | 0 0 | <- | Busy | 0 0 | 1 0 |
| 1 0 | 1 0 | <- | Answer | 1 0 | 1 0 |
| 0 0 | 1 0 | -> | Clear Fwd. after Ans | 1 0 | 0 0 |
| 1 1 | 1 1 | <-> | Blocking | 1 1 | 1 1 |
SLM Signalling bit states
| Tx | Rx | Direction | Signal | Tx | Rx |
| A B | A B | | | A B | A B |
| 1 1 | 0 1 | <-> | Idle | 0 1 | 1 1 |
| 1 0 | 0 1 | -> | Seizure | 0 1 | 1 0 |
| 1 0 | 1 1 | <- | Seizure Ack | 1 1 | 1 0 |
| 0/1 0 | 1 1 | -> | Decadic Dialing | 1 1 | 0/1 0 |
| 1 0 | 1 0 | <- | Subscriber Free | 1 0 | 1 0 |
| 0 0 | 1 0 | <- | Ring | 1 0 | 0 0 |
| 1 0 | 0 0 | <- | Subscriber Busy | 0 0 | 0 1 |
| 1 1 | x x | -> | Clear Forward | x x | 1 1 |
| 1 0 | 1 0 | <- | Answer | 1 0 | 1 0 |
| 0 0 | 1 0 | -> | Clear Fwd. after Ans | 1 0 | 0 0 |
| x 0 | 0 0 | <- | Clear Back | 0 0 | x 0 |
| 1 1 | 1 1 | <-> | Blocking | 1 1 | 1 1 |
SLM signaling is used from toll to local connections (Operator call) and ringing cadence is supplied by the originating side. If the called party is engaged in a call, it is intruded by the calling operator.
