Tricks of the telephony trade

All PABX systems start ignoring the digits dialled after a preset duration where no further digits are dialled. One reason for this is telephone banking. Users dialling their bank will need to enter a PIN to access the account. The PABX manufacturers certainly do not want to output this confidential information to the telephone management system (TMS), so these digits will not be featured on the TMS report.

Another reason certain digits are ignored is that the PABX may need to route calls in a particular way depending upon the dialled digits. For example, least-cost routing premicells will only take cellphone numbers or international call-back will only take international calls. The PABX system needs to ensure the calls go down the correct lines.

The PABX will wait until it "thinks" it has all the dialled digits and then route the call down one or another trunk line.

Once the PABX thinks it has all the dialled digits it will stop recording the numbers dialled and get on with the job of connecting to the correct extension. Anything dialled later than this will not be recorded and will not be sent to the TMS.

The problems start when employees become aware of this aspect of the relationship between the PABX and the telephone management system.

John Bannister, IT director at Multimatics

The problems start when employees become aware of this aspect of the relationship between the PABX and the TMS. An employee could dial "08" and then wait for a certain amount of time before the rest of the number is dialled. The result is that the TMS will receive a call record where the dialled number is only 08. It does not have the rest of the dialled number and cannot tell whether:

* It was a cellphone call (eg, 082)
* A competition line call (eg, 08622)
* A shared revenue call (eg, 08674)
* A toll-free call (eg, 0800)

Most telephone management systems will simply ignore a call with such a short dialled number. It is one of the easiest ways for an employee to bypass the TMS.

This can lead to larger problems. For example, should an employee "own" that 08673 number and is sharing the cost of the call (R3.90 per minute, plus VAT) with Telkom - at your expense! Alternatively, the employee could simply be frequently phoning a friend on their cellphone and deliberately avoiding getting into trouble for doing so.

* If the TMS has the facility to do so, make sure it does not ignore short dialled numbers.

* If it does not have the facility, it will usually be able to output the call records to a plain text file or a comma-separated variable file. Users should be able to open these with a spreadsheet and sort by the column which has the dialled number. This will allow the company to see if any extensions are consistently dialling these short numbers.