I have just had a call from a local entrepreneur who has been a customer for almost 20 years.

He wanted advice on whether a proposed new digital cordless phone would work on his office phone system and in particular whether the SMS text message function would work.

My customer had his eye on the Siemens Gigaset SL785 digital cordless phone.

I advised that the SL785 would certainly be able to make and receive calls when connected to an extension of his Panasonic phone system.

I also advised him that it could also transfer calls to other extensions.

However, I knew that his office phone system would cause some problems for the SL785′s SMS text message function.

Fixed line phones (such as the SL785) that have an SMS function send SMS text messages via an SMS Gateway which stores the message before forwarding it to the mobile phone networks or to other SMS Gateways.

A fixed line phone with SMS text message capability would simply dial the phone number of an SMS Gateway when it wants to send an SMS text message.

This phone number would usually be a premium rate number since this is how most SMS Gateway service providers make their money.

When an SMS Gateway answers a call the SMS fixed line phone transmits the SMS text message to the Gateway.

One or more SMS Gateway phone numbers are usually pre-programmed into SMS fixed line phones.

The problem is that on a phone system it is usually necessary to dial a prefix such as “9″ in order to seize an outside line.

An SMS fixed line phone would usually not have any of its pre-programmed SMS Gateway phone numbers prefixed with a “9″ since all manufacturers would assume that the phone is going to be connected directly to a phone line and not to a phone system extension.

The good news is that after a quick check of the Siemens Gigaset website I discovered that it was reasonably easy to modify the pre-programmed SMS Gateway phone numbers and therefore add the “9″ prefix.

I was therefore able to advise that it would be possible to to send SMS text messages using the SL785.

However, I had to advise that it would not be possible for the SL785 to receive text messages.

The reason for this is that the in order to deliver an SMS text message an SMS Gateway must be able to dial directly an SMS fixed line phone (such as the SL785) and also deliver Caller ID information to the SMS phone.

Even if the phone system extension to which the SL785 is connected is programmed to ring immediately for incoming external calls the Panasonic phone system that is installed at Chris’s premises can’t pass Caller ID information to extension phones.

The reason that Caller ID information is essential for fixed line SMS text message services is that an SMS phone must be able to recognise the Caller ID of its SMS Gateway.

When the SMS phone recognises that an incoming call is from an SMS Gateway the phone would automatically go into receive mode for an SMS text message rather than a regular phone call.

When the SMS phone answers the call it immediately recieves a data burst containing instructions on how to receive the SMS.

If the calling party has paid for the text message then the SMS Gateway immediately delivers the message to the SMS phone in another data burst before disconnecting the call.

If the called party is to pay for receiving the text message then the SMS Gateway immediately disconnects the call.

The SMS phone would then initiate a a call to the SMS Gateway to collect the waiting SMS.

It is important to note that when a call is received from an SMS Gateway the SMS phone would not ring.

An SMS text message call is therefore unnoticed by the receiving party until the message waiting light starts flashing on the SMS phone.