What is Short Message Service?
Fax and data transfer are familiar services from the fixed telecom net. The GSM-nets additionally offers a practical service called SMS (Short Message Service). As you can understand from the name, it is a service used to send short messages directly to GSM cell phones. This is done without any extra equipment. A modern cell phone is all you need. An SMS is, due to the low costs, an alternative to making a phone call.
Maximum 160 characters.
A maximum of 160 characters or 140 byte per message can be contained in such a message. Messages can also be linked together to form a longer message. There is a difference between SMS-MT (mobile terminated) which is sent to the GSM phone and SMS-MO (mobile originated) which is sent from the phone. Receiving an SMS is possible with almost all GSM phones. Sending is possible with most new phones. You have to program the number to your message center (SMSC) of your net operator in to your GSM phone. If your phone is turned off the SMS can't be received. The message will then be stored in the system in a couple of days (varies from operator to operator) and will be sent when the phone is turned on again. The person sending the SMS doesn't really get any confirmation of reception. You will always have to pay for sending SMS's weither it is received or not.
Extra SMS services.
Most operators offer their customers the possibility of retrieving information to their own GSM phone by the means of SMS. You will then send a speciell message to a speciell phone number. In a while you will receive an SMS which contains the information you have requested. It might be about the stock market, weather, train or flight departures, exchange rates, sports results and much more.
Four ways of sending SMSs.
Confirmation of succeeded transmission
Net operators and service providers has added the possiblity to have a confirmation sent to the sending party when the message has successfully reached the receipent. The method is similar between operators. Most phones have a setting for this, or you add a code in the beginning of the message. For example with Swedish Telia you add *kv#.
Sending and receiving SMSs in other GSM countries almost always works fine. Maybe sometimes you will have to alter the number of the readily programmed message center (SMSC). Normally you should use the SMSC of you own net operator. Your operator must, of course, have roaming agreements with the nets you are visiting. Sometimes it is not supposed to work. But you might solve theese problems by entering the number of another net operator's SMSC.
An example from real life: A customer of Swedish Telia was in Slovenia in the Mobitel net. All details about the roaming was not quite ready yet. He couldn't send SMSs. The customer entered the SMSC number of another Swedish operator, Comviq. This is not supposed to work, but it did.
Another example: A customer of Swedish Comviq was in Lithuania in the Bite net. He couldn't send SMSs. The customer entered the SMSC number of Satelindo (Indonesia). It all work just fine.