Cti Communications Ltd
Call us now for IT support and free advice
01242621621    01242621666  

sales@cticom.ms   support@cticom.ms

5100 SIP to ISDN converter - ISDN to SIP gateway

SIP to ISDN converter

Our SIP to ISDN converter will let your ISDN phone system connect to VoIP - just plug it in. If your current ISDN phone system doesn't support SIP VoIP and you want to take advantage of cheap VoIP phone lines or any VoIP service without changing it then you need a SIP to ISDN converter / ISDN to SIP converter (SIP gateway). Unplug from your BT ISDN box(es) and plug into the converter, your phone system doesn't know anything has changed.

We will configure the SIP to ISDN converter / SIP gateway with the details of your chosen SIP VoIP provider, you unplug from the ISDN & plug into the SIP VoIP to ISDN converter and start saving money.

It is by far easiest to implement as well as the cheapest non DNS SRV ISDN system to SIP converter

There is a carrier issue where if a DDI is called via some mobile networks and the user on your phone system has set their calls to forward to an external number the caller may not hear ringing before the person answers.

Select the correct unit below to match your type of ISDN & the number of channels.

ISIP 8 - 1 BRI (2 channels) 240
ISIP 8 - 2 BRI (4 channels) 300
ISIP 8 - 3 BRI (6 channels) 320
ISIP 8 - 4 BRI (8 channels) 420
ISIP 30 - 10 channels 660
ISIP 30 - 20 channels 840
ISIP 30 - 30 channels 960

You will need us to set it up and configure it for 20.


ISDN to SIP Converter

Zero Configeration

You do zero configuration on the unit, we will do for you, to program the converter we will need to know:

  1. SIP account details as supplied by your provider
  2. Public IP address the ISDN to SIP converter will present when making calls
  3. The IP address / subnet / gateway it will use when in operation
  4. The number of "digits to line" your phone system is setup to receive
  5. The area code that people omit when calling local numbers
  6. The number it should present when no presentation number is provided

Set the Firewall Rules

You will need to enable SIP and RTP port forwarding in your firewall, and lock them to your VoIP exchange. In a Draytek 2860 or newer this takes 20 minutes, if you want us to do this for you we can and will charge our normal support rates.

Ports Locked to VoIP Exchanges

CTi Remote Support

For support we access the system via https on port 443 and SSH on port 22, this can be via NAT either way these should be locked down to our IP addresses:

giga.cticom.ms83.151.207.90
aa.cticom.ms81.187.212.167
Support Ports

On other routers it may take longer to set things up.


When ready to test

  1. We will program it with the details provied by your VoIP provider and the public IP it will present.
  2. We will program it with the IP address / Subnet / Gateway / you have reserved on your network for the 5100 iSIP VoIP to ISDN converter.
  3. Unpack the 5100 iSIP ISDN to SIP converter and adaptor(s).
  4. Plug from the LINK port on the 5100 iSIP sip to isdn converter into a port on your network, Plug in the power supply and turn on.
  5. Check the port forwarding rules in your firewall are set to the SIP to ISDN converters IP address.
  6. Look at that IP address in a browser and see if it is showing registered at the exchange.
  7. If registered, plug the adaptor(s) into the PRI or BRI port(s) on the SIP to ISDN converter.
  8. Unplug your phone system's ISDN cable(s) from the BT box.
  9. Plug your phone system's ISDN cable(s) into the adaptor.
  10. Look at the ISDN to SIP converter IP address in a browser and it should show it is connected to your phone system.
  11. Try a test call, via the browser page you will see what is currently in progress and the number of calls seen on the ISDN and seen on the VoIP SIP connection.

How to connect 5100 iSIP converter to phone system


All prices exclude VAT, and were correct on 29/09/2023 16:18:46 , but should only be used as a guide.