The VoiceBox appears to the computer as a single IO mapped port, at the IO address FF7F Hex, or 65407 Decimal.
The input port responds with the VoiceBox signature of 24 on its uppermost 7 bits, and the Least Significant Bit (LSB) is the BUSY status of the VoiceBox.
The VoiceBox must be sent a silence code (0) at the end of each word, or the last allophone will be repeated indefinitely.
For full handshaking operation, the VoiceBox should be driven as shown in the following BASIC procedure:
DEFPROC speak allophone
Is VoiceBox connected? IF IN 65407 BAND 254 <> 24 THEN PRINT "Not Connected": STOP
Wait until not busy DO: LOOP UNTIL NOT IN 65407 BAND 1
Output the allophone. OUT 65407,allophone
Where allophone is the number of the required allophone from the table.
Rumour has it that no commercial software at all was released to use the Voicebox. The only known examples are the talking clock on Fred 17 and Immortal Combat on Fred 59 - if you know different then update this entry!