Telephone Hybrids or Talkshow Systems convert an incoming phone call into an Audio signal which is suitable for the studio environment. There are typically three different line interfaces that are used: POTS (analogue telephone lines), ISDN or Ethernet interfaces using the Voice over IP technology.
ISDN and VoIP are digital transmission procedures which do not cause any line echoes. However, POTS lines as well as POTS telephones in combination with ISDN or VoIP lines can cause line echoes resulting from the 2-wire technology or the conversation from 2- to 4-wire technology. These echoes are disturbing and must be eliminated by line echo cancellers. The AVT systems take care of this problem by having its own echo canceller for each caller line to achieve the best possible speech quality – even in caller conferences.
Whereas POTS and ISDN are already about to be switched off in some countries, VoIP is the standard nowadays and in the future. All AVT Systems support the VoIP operating mode, either in the standard delivery mode, or they can be extended later on by software upgrade so that the user does not have to reinvest in a new telephone hybrid when changing from e.g. POTS to VoIP.
To use the AVT telephone hybrids in VoIP operating mode, for each caller line a SIP account is required. With these accounts the system can register at a SIP Server (which can be e.g. your IP PBX or also a SIP Server on the internet).
VoIP offers a big advantage compared to analogue telephone lines – the so-called HD Voice feature. HD Voice means 7-kHz speech quality (G.722 coding algorithm). Normal telephone quality only offers 3.1 kHz. With the AVT Telephone Hybrids you can also benefit from this feature. Nowadays, almost all standard IP telephones and also DECT telephones support HD Voice. Of course, an HD Voice connection can only be established if both sides support it.