SMS PDU-Mode
Flash SMS

On some phones (all Nokias, some Siemens, Ericsson, Motorola etc..) a class 0 message will appear as a flash SMS message. These messages appear on the screen immediately upon arrival, without the need to press any buttons on the phone. If the data coding scheme is set to 16-bit unicode (ucs2), and the message starts with "0001", it will appear as a blinking flash message.

Octet	Value	Description
TP-DCS	18	16 bits (UCS2), message class 0
TP-VP	AA	Validity period
TP-UDL	0C	User Data Length, 12 octets
TP-UD	00 01 00 41 00 6C 00 65 00 72 00 74	User Data, message "Alert"

This table shows some relevant octets in a flash SMS message. The first unicode character ("00 01") enables the blinking. The maximum length of such a message will then be 69 unicode characters.