As shown in an earlier post, the Data Coding Scheme (DCS) octet in the SMS PDU can be used to turn a regular text message into a flash message.
Another feature of SMS that is enabled through use of the DCS is the Message Waiting Indication:
- When someone leaves you a voicemail, the voicemail system communicates with the SMSC to send your phone a special SMS message that turns on the little icon on your phone that indicates that you have a new voicemail.
- When you listen to your voicemail, the voicemail system also communicates with the SMSC to send your phone a SMS message that turns the little icon off again.
Using the DCS you can turn the voicemail icon on or off yourself.
This is an example PDU to set a voicemail indication:
Here is what the individual octets represent: