Mail-A-Voice model BK-503 | The sound machine

Описание: This month's sound machine is the Mail-A-Voice BK-503. The device made it possible to magnetically record short audio content onto special flexible discs that could then be easily folded and mailed like a normal letter, but with sound.
Produced by 'The Brush Development Company' (Cleveland, Ohio), it approached sound recording on a magnetic medium in a completely new way. Its sound carrier is a flexible disc 23 cm (9 inches) in diameter, in which the sound track is a spiral from an inner diameter of 13 cm (5 inches) towards the outer edge. The sound track has a width of 0.35 mm (0.014 inch) and the pitch of the spiral is 0.6 mm (0.025 inch). Despite the close spacing there is no crosstalk between the tracks.
The turntable rotates at 20 rpm, while the record has a total recording time of just over 3 minutes. The Mail-A-Voice model BK-503 was produced around 1948-1950.
The Swiss National Sound Archives owns a specimen of the device, which it restored in its technical workshop, significantly improving the sound reproduction.

Editing and directing Gabriele Franzoso
Script Giuliano Castellani

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