| Key | Frequency |
|---|---|
| 1 | 697 + 1209 |
| 2 | 697 + 1336 |
| 3 | 697 + 1477 |
| 4 | 770 + 1209 |
| 5 | 770 + 1336 |
| 6 | 770 + 1477 |
| 7 | 852 + 1209 |
| 8 | 852 + 1336 |
| 9 | 852 + 1477 |
| * | 941 + 1209 |
| 0 | 941 + 1336 |
| # | 941 + 1477 |
| Meaning | Frequency (Hz) | On Time (sec) | Off Time (sec) |
|---|---|---|---|
| Dial | 350 + 440 | Continuous | |
| Busy | 480 + 620 | 0.5 | 0.5 |
| Ringback, Normal | 440 + 480 | 2.0 | 4.0 |
| Ringback, PBX | 440 + 480 | 1.0 | 3.0 |
| Congestion (Toll) | 480 + 620 | 0.2 | 0.3 |
| Reorder (Local) | 480 + 620 | 0.3 | 0.2 |
| Receiver Off-hook | 1400+2060+2450+2600 (loud) | 0.1 | 0.2 |
| No such number | 200 to 400 continuously modulated at 1 Hz | ||