| Software programmable parameters for global compliance with one hardware design: |
| Constant current loop feed (18–45 mA) |
| Two-wire ac impedance |
| Transhybrid balance |
| Ringing frequency, amplitude, cadence |
| Loop closure and ring trip thresholds |
| Ground key detection threshold |
| Low standby power consumption: <65 mW |
| Loop start and ground start support |
| Automatic switching of up to three batteries |
| DTMF generation and decoding |
| Modem/fax tone detection |
| Internal ringing up to 65 V RMS (Si3220) |
| 12/16 kHz pulse metering (Si3220) |
| FSK (caller ID) tone generation |
| PCM/SPI or GCI digital interfaces |
