Blinking messages can be encoded using UCS2 encoding. Use 00 01 (hex bytes) as a toggle for blinking. This is just an additional feature that works only on some older phones.
Flash messages show up on the user interface of the phone just after receiving. Messages that are sent with class 0 data coding scheme are treated as flash messages by the phone. These messages are not automatically stored to the phone.
BR
M, Forum Nokia