Every Short Message has to pass the SMSC. There are different ways to tranfer the Short Message to the Short Message Service Centre. A Short message can reach the SMSC by GSM modem / module and can be transferred to an email or fax.
Make a call to a manual reception and tell them what you want to sent and to whom. Not very useful in industrial GSM applications.
Make a call to an automatic answering service and make a choice from a number of ready made texts. Not popular in industrial applications also.
Use your own GSM phone with sending abilities and enter a message and send it. Can be useful, if you have to send control commands from somebody to a machine, to change parameters. Most GSM phone offers the storage of Short Messages so that you can send from memory of the SIM card.
Use a computer with a PSTN modem and a special SMS program. Popular for the sending of Short messages to mobile GSM phones. There are a lot of local SMS programs available. A few of them are freeware and others are shareware. In Germany ( and other countries) the GSM operators offers light versions of SMS programs as freeware. If you have a need for software that have more features, then you have to buy it. If you use a local SMS software, then it is in local language and the parameters are set for your GSM operators. The other technical problem are the different hardware interfaces like PSTN modem or Datex P ( X.25) and the different software protocols like TAP and USP on the SMSC. If you have to send only then TAP is OK, but if you have to send and to receive then UCP is the right way. The UCP can send and receive Short Message. The easiest, but not fastest transmit and receive you can reach with a GSM modem. A GSM modem can send / receive a Short Message each 6 to 10 seconds. With a connect based on UCP you can reach 600 messages per minute.
For industrial applications you can not often not use ready SMS software. You have not to think about the protocols, if you buy software drivers from third parties. That can save time and money.
SMS to fax is available by a lot of GSM operators and by local third parties.
SMS to email is available by the GSM operators and by third parties too.
Email to SMS is available by the GSM providers and by third parties. A few of them offers that serif free of charge, but with advertising on the end of the message. Such free of charge services do mostly not free of charge for commercial GSM solutions.
In the beginning of GSM it was not possible to send an SMS from GSM operator A in Germany to GSM provider B in Germany. A few companies has developed special services to bridge that. They offer sending to “foreign” German operators. Right now they offer a couple off other specials, that are not supported by the local German operators.
There are different ways to send or to receive a SMS. The simplest with a GSM modem. Unfortunately, a GSM-Modem can process only 6 to 10 SMS per minute. To increase the speed a connect to a communication server with up to 32 GSM modem is neccesary. Then becomes possible with it up to 320 SMS per minute. With this kind of SMS communication none direct connect to SMSC is necessary. Some GSM operators offer no direct connect. Consequently, the communication server with 32 GSM modem is a good alternative.
Faster and more comfortable is the direct link to the SMSC. With a direct acces you can reach up to 600 SMS per minute. Popular protocols are UCP, SMPP, CIMD2, OIS and TAP. TAP is an old protocol to the send messages to a pager. Causes historically, TAP offers sent of messages from server only. With which hardware the SMSC can be connected is not the same by all the different operators. The exact data must be asked at the GSM operator. The parameters are not equal also. Through the variety, the likelihood of a mistake is very large.
For the world wide market, there is a big number of software to ease the direct access to SMSC. The offer is from Freeware, Open Sources up to software which almost all types of the communications masters. With Freeware, there is usually no support. The protocols named above are developed further continually. So constantly changes on the software is necessary. The following graphics shows an example for a software which at many companies in the usage. Many settings of GSM operators already in the default parameters. Further new operators are added by the developer usually free of charge. The functions of the software and service / support is perfect.Whoever nevertheless thinks to save money with own drivers finds the sources of the known protocols in the appendix. There are still students, which must develop drivers itself.