Fixed Cellular Terminals (FCTs), are devices typically used with private telephone systems for least-cost routing purposes. Essentially a mobile phone, these devices can be connected to a trunk port on a PBX to route calls made from desk extensions to mobile numbers over the cellular network rather than via the landline provider, a mobile-to-mobile call being cheaper than a landline-to-mobile call.

These devices can also be used to provide voice and fax telephone services in remote or temporary locations where fixed line services may be costly or not required, such as a port-a-cabin on a building site.

When troubleshooting PBX connectivity or routing issues, the PBX should be addressed last - firstly verify that the FCT itself is working correctly. People are typically confused by these devices but when troubleshooting them it is important to treat them exactly like a mobile phone and not to forget the basics.

LEDs

What are the lights on the unit doing? Unlike a phone these devices do not typically have screens so you cannot tell at a glance what they are doing, you will need to note down the LED sequence and consult the user manual to see what that means. Check the following:

• the SIM is inserted correctly
• the device is receiving adequate signal
• the device is registered with the mobile network
• the SIM is live

The easiest way to verify that the FCT itself is working correctly is to connect an analogue handset (ie, a desktop phone) directly into the unit and verify that you both receive a dial tone and can place a call successfully. If you receive any sort of recorded message from the operator then you should pay attention to what it says and if necessary contact customer services.

Connectivity

Provided that a connected handset works correctly, verify that the FCT has been connected to the PBX correctly. The vast majority of devices only work in trunk mode: it is not possible to connect the unit to an extension port and assign the unit an extension number. Rather devices must be connected to an analogue extension ports and routing entry created to pas all numbers beginning "07xxx" via that trunk.

Call Termination

One area that can sometimes require additional configuration is that of call termination - situations can arise whereby one call can be placed through the FCT successfully, but following the termination of that call, the trunk is then available for a following 30 seconds or so following the termination of that call - meaning that no subsequent calls can be routed over that trunk until it then becomes available again. This is typically caused by the fact that the FCT is not receiving or is not correctly interpreting the termination command being sent by the PBX.
PBXs are typically configured to signal the termination of a call either by reversing the polarity of the circuit, or by sending a specific tone. If calls are not being closed correctly, then the precise configuration of what the PBX is sending needs to be ascertained, and then determined whether or not that is supported by the FCT.

Other problems and solutions

Typically FCTs live in server rooms or comms cabinets and are not checked on a regular basis. Should a device suddenly no longer route calls or provide a dial tone, check the LEDs on the unit. If a unit has been receiving SMS messages (spam messages, wrong numbers or network marketing updates) and these have not been being cleared down, should the internal memory on the unit fill up, the unit will no longer be able to place calls until these messages are deleted. This usually involves connecting a phone to the unit and entering a system command on the keypad.