ISDN PRI

ISDN PRI stands for integrated services digital network primary rate interface. This service is used primarily by large organizations with important communications needs or by companies who are not willing to compromise on voice quality. It uses T1 technology for transport. It’s is still organized as 24 channels on a single digital phone trunk, but one of the channels (the D channel – “Data channel”) is used exclusively for call control and signaling, leaving the other 23 channels (the B channels – “Bearer channels”) for the transport of digitized voice.

ISDN is the technology which is responsible for the outstanding land-line voice quality we’ve been accustomed to since the late 80′s. It’s a proven technology and, to this day, the only way to guarantee voice quality. This is because ISDN is a circuit-switched technology, which means that bandwidth for each call (64Kbps) is reserved for the duration of the call, unlike VoIP, which runs on IP – a packet-switched protocol lacking the ability to allocate bandwidth on a per-channel basis which simply attempts to satisfy all traffic by prioritizing it.

The main advantage of ISDN over a basic T1 trunk is that the voice channels on a PRI are allocated dynamically and each call can have its own Caller-ID information (whereas each of the 24 channels in a T1 trunk has a pre-assigned Caller-ID number which cannot be changed without our intervention)

We offer ISDN PRI service all across Quebec and Ontario. Variations include:

  • BIDI ISDN PRI (23B+D) – Standard Bidirectional Service, 23 channels open
  • INBOUND ISDN PRI (XXB+D) – Inbound Service only, up to 23 channels can be open
  • Asymetric ISDN PRI – Bidirectional service, channel limitation inbound/outbound

In all cases, calling key restrictions apply.