Why can’t I make or receive ISDN2 calls using my Gigaset DX800?

I was contacted by an office manager who had recently purchased a Gigaset DX800 ISDN2/VoIP DECT cordless phone system. His problem was that, although he could make and receive VoIP calls without any problem, he was unable tomake or receive any calls via the DX800 ISDN2 connection.

He was getting nowhere with Gigaset support or BT support so he contacted Premitel.

From past experience I knew that the likely cause of the problem would be a mismatch betwen the ISDN2 configuration at the Exchange and the ISDN2 configuration required by the Gigaset DX800.

I was aware that the DX800 required a Point-to-Multi-Point ISDN2 connection and that, unless specifically requested, BT usually supplied Point-to-Point ISDN2 connection.

Therefore the first thing that I had to establish was what type of ISDN2 configuration had been supplied by BT.

As expected it was the wrong type.

I advised the office manager to contact BT and request a change in his ISDN2 configuration to Point-to-Multi-Point.

This was done almost immediately and that solved my client’s problem for making outgoing calls, but he was still unable to receive any incoming calls.

To receive incoming calls it was necessary to configure the DX800 to accept the direct dial numbers that had been allocated by BT for the ISDN2 connection.

The direct dial numbers on a Point-to-Multi-Point ISDN2 connection are called Multi Subscriber Numbers (ie MSNs) and are configured differently from the more usual Direct Dial In (ie DDI) numbers that are associated with Point-to-Point ISDN2 connections.

Configuring the DX800 for MSNs was relatively straightforward and was similar to configuring DDIs in PBXs in that only the last 6 digits of each number had to be specified rather than the full 11 digits.

After configuring the DX800 for 3 x MSNs my client was delighted to have a fully working phone system within one day of contacting Premitel, but over 6 weeks after purchasing the Gigaset DX800.

Get in touch with Premitel if you have a specific requirement or if you wish to discuss how your business could make better and more cost-effective use of its existing telecommunications and internet infrastructure and services.