Sony Ericsson GM47 - Manual (Page 285)

15. SHORT MESSAGE SERVICES - POINT TO POINT
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LZT 123 7263 R1C
Note! The Ring Indicator will always be active for incoming calls independent
of this setting.
<n> Description
0 RI is disabled for incoming SMS messages. Default value
50-1150 RI is enabled for incoming SMS messages. Pulse duration
selectable between 50 and 1,150ms inclusive