Connecting DECT Phone Systems to VoIP Networks

Patton SmartNodes use a High Precision Clock to enable DECT Phone Systems to connect to and interoperate with SIP Trunks and VoIP PBX Systems, including on-premise and Cloud-based systems.

The Problem
The ISDN telephony network provides an 8 kHz clock signal to all connected equipment. This clock is ultra-stable, precise and derived from an atomic master clock in the Network. DECT base stations derive the DECT base frequency from this Clock. Migrating DECT systems to VoIP requires that clock frequencies be as precise and reliable as the clocking in the ISDN network. Here is Patton's solution for integrating DECT systems to VoIP Networks.

The Picture
A DECT PBX system is clocked from the atomic master clock. PBS manufacturers do this so they don't have to include in their system an expensive frequency generator for the DECT base frequency. When migrating to SIP, use a SmartNode version with internal clock accuracy to Stratum 3 as source for the DECT frequency.
The Solution
  • Patton SmartNodes offer high-precision clocking schemes to enable DECT systems to be connected to VOIP networks on campus and to IP or TDM based telephony networks.
  • Patton's SmartNode clocks are standardized to an accuracy of 50ppm
  • Through the most flexible clocking configuration in the industry on SmartNodes, it is possible to select any ISDN port as clock source. The clock from the clock source is then distributed to all other ISDN ports. Thus it is possible to either keep one public ISDN line as clock master, or to feed a clock signal from another source to the SmartNode.
  • Through use of the new high precision models, SmartNode delivery internal clock accuracy to Stratum 3. This is very precise and way enough to serve as source for the DECT frequency.
The Details
DECT Telephone Systems deliver high-quality wireless voice communications to employees who roam within a building or campus. Popularized in Europe, DECT systems enable low cost, high quality, cordless telephony (using a single base station to connect one or more handsets to the public telecoms network). Enterprises have also deployed DECT systems including a cordless PABX, where calls can either be within the system or to the public telecoms network. Every major PABX vendor offers DECT access options. DECT can also be found in baby monitors, electronic cash terminals, traffic lights, and remote door openers.

The ISDN telephony network provides an 8 kHz clock signal to all connected equipment. This clock is ultra-stable, precise and derived from an atomic master clock in the Network. DECT base stations derive the DECT base frequency from this Clock. So what happens when an enterprise moves to VoIP? The Gateway installed now provides clock to the PBX - and thus, the DECT base frequency is derived from the Gateway.

Is this an issue? Yes it is. Most VoIP equipment manufacturers have not produced products which can interoperate with DECT because they have not considered the need for a High Precision Clock. The result is that the DECT frequency is not precise enough to generate a DECT base frequency and therefore the handset will not registered to the Base Station.