Almost all onboard computers use modems which are very similar to your mobile phone, in fact they use exactly the same SIM card that is in a standard mobile phone. There are three basic ways in which a mobile phone can send and receive data. The first is DDC which stands for Direct Data Call, this is just the same as using your mobile phone to talk to someone, it is a direct call from one phone to another except it is sending data instead of voice. The second is called GPRS and stands for General Packet Radio Service; this is a very fast and efficient way of sending and receiving data over the internet using a standard mobile phone. The last method of sending data over a mobile phone is familiar to all of us, it is sometimes dubbed as texting but its proper name is SMS which stands for Short Message Service and as its name implies it is short, just 160 characters.

The way we measure data is by counting the number of bytes (or characters) in the data. Just look at the difference in the cost between these three different ways of sending data over your mobile phone.

A DDC call will send data at 9600 b/sec so if you are paying 10p per minute for your mobile call it will cost you £1.45p to send a megabyte of data. GPRS is charged differently, with GPRS you don't pay for the amount of time you are connected, in fact you are always connected, you simply pay for the amount of data you send. A normal GPRS contract will cost you around £11 for 5 megabytes of data, so the cost per megabyte is £2.20. Now look at the cost of SMS messages when worked out to a per megabyte charge, an SMS message is only 160 characters long and you can pay up to 10p per SMS message, so the cost per megabyte works out to £655.36. Yes that's right six hundred and fifty quid per megabyte instead of just around two quid for DDC and GPRS!

Now you would think that hardly any onboard computer provider would use SMS for sending data but you would be wrong, in fact almost all of the truck manufacturers systems are based on SMS as well as most of the third party providers. This is barmy not only because of the outrageous cost but also because of the fact that SMS messages are exactly what their name implies, short. Too short in fact to be able to handle full collection and delivery addresses and consignment details. So why do truck manufacturers and onboard computer companies use SMS? Well it's a ready made messaging service that they can easily tap into without having to write much software. In other words to make life easier for themselves they have chosen a communications method that will cost you £650 per megabyte instead of just £2. That just isn't good enough!