Compact helium speech unscrambler using charge-transfer devices

Helium speech is the term commonly used for the distorted speech uttered by deep-sea divers breathing in a helium/oxygen mixture. Present unscrambler designs use pitch synchronous time-expansion signal processing with digital storage. The compact unscrambler reported here has been configured using analogue charge-transfer devices for waveform storage and c.m.o.s. digital circuitry for control logic as a precursor to development of the whole system as a single integrated circuit. The compact unscrambler itself is shown to offer distinct engineering and operational advantages.