The actual text of the SMS message isn't the only thing that's being transmitted. Here are the elements of a complete SMS transaction:
- Header: identifies the type of message.
- Service Center Timestamp
- Originator Address: the phone number of the sender
- Protocol Identifier
- Data Coding Scheme
- User Data Length: tells how long the message is
- User Data: the message itself (140 bytes: 160 7-bit characters, or 140 8-bit characters)
When you send an SMS to an email address, the message is still sent to the SMS Email center, but then it is relayed to the email server of the recipient. The recipient's email address is actually embedded in the User Data portion of the message, transparently on a Treo, or manually on a VisorPhone.
7-bit vs. 8-bit messagingCurrently, most North American wireless service providers support the 7-bit alphabet. Some providers support 8-bit messaging, which enables people to send small image files with a message. If you are receiving garbled strings of text as SMS messages, someone is probably trying to send you an 8-bit message with an image or ringtone, and your wireless service provider only supports 7-bit messaging.
