Sony Ericsson GS64 - Manual (Page 73)

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5.21 Ringer Output (BUZZER) [to be implemented in a future release]
Pin Name Direction Function
52 BUZZER Output Buzzer output
Connecting the BUZZER signal to an inverting transistor-buffer followed by a
piezoelectric transducer enables the wireless modem to play pre-programmed
melodies or sounds.