Our messaging application sends SMS text notification messages over SS7 per the GSM 3.40 standard. When testing with a Nokia
phone we notice that the voicemail icon and counts are displayed
as we hoped but when we set the fax count (by sending an
SMS Deliver message with a nonzero fax count in the user data
header), the fax icon is not removed when we subsequently
send another message with a zero in the fax count. The voice
mail icon seems to work OK. Can someone suggest what we
might be doing wrong?
Here are some additional details:
1. We set the coding group bits (7..4) in the data coding scheme
to 13 (1101) when we want to set the icon. We set bit 3 (the icon
indicator) and we always set bits 0..1 to 0 (voice mail).
2. When want to turn off the icon we set bits 7..4 to 12 (1100) and reset the icon indicator. Again bit 0..1 are always 0.
3. We always send the header and we always send all 4 counts
in the header. We assume that the Nokia 3590 "sees" the nonzero fax count and sets the fax icon even though we never
set the fax message type in the Data Coding Scheme octet
above. However it doesn't appear to reset the fax icon when
we send a message with a zero fax count.