The Versa-Link is an automatic call processor that routes calls based on Comfort Noise Generator (CNG) and Dual-tone Multi-frequency (DTMF) tones to phones, a fax, modem, or any other device. Dip switches on the device allow for easy programming. This call switch can also be used with any Selective or Distinctive Ring Service offered by local telephone companies in North America.  In Selective Ring mode, the unit will route inbound calls to the appropriate device based on the ring cadence of each distinctive ring number. Barge-in protection keeps your data transmission free from interruption. A busy signal is heard when other devices attempt to use the outgoing line.