Subscriber Signaling

Supervisory signaling:
- On-hook. Connection between tip and ring is broken.
- Off-hook. The phone connects the wires.

Ringing: Alternating current (AC) on wires makes phone to ring.

Informational signaling:
- Dial tone
- Busy
- Ringback
- Congestion
- Reorder
- Receiver off-hook
- No such number
- Confirmation

Address signaling:
- Pulse
- Dual-tone multifrequency (DTMF)