Voice scramblers FX118 and PCD4440

Owing to the vast increase in the number of mobile telephones, there is an equally vast demand (and need) for means of making listening to third-party telephone conversations impossible, or at least difficult. Two such means are introduced here; both are compact and require only low power. One is based on the Type FX118 IC from Consumer Microcircuits Ltd (CML) in England and the other is the PCD4440 from Philips of Holland, which is programrnable via an I²C bus.