On an idyllic retreat to a mountain cabin, Enola Ranson accidentally breaks a lamp and discovers a covert listening device. Persuaded by her horror writer husband, Guy, who is intrigued by the analog transmitter, they set out to solve the mystery.
Strange wiring inside the cabin, hidden recordings, a mafia past, a shady private detective, a boy witness, and an eerie modulation noise are all clues to past murders. Time is running short as an escaped lunatic is on the loose, finishing what they started and stopping anyone who knows.
Will Enola and Guy uncover the secrets of the past, or will they become the next victims?
If you hear the sound, it is too late.
SRT-91 — a covert listening device (transmitter) with DP audio masking. It consists of an RF (radio frequency) module and video coder (audio masking unit) and is housed in a rectangular (13.5 x 22.5 x 110 mm) metal enclosure.
DP — Dirty Pulse audio masking technique based on Pulse Position Modulation (PPM) in which the intelligence is conveyed by varying the time relationship of the pulses of the wave. In this scheme samples are taken at fixed intervals and transmitted as PPM. Under control of a noise generator, the back porch of each pulse is delayed by a randomly determined value. Only the relative position of the front porch contains intelligence.
SRR-90 A/B — surveillance receiver for the reception of various covert listening devices with a modular design. A is an upright version and B is a flat version.
SRR-145 — down-converter. It converts analog signals between lower and higher frequencies, extending the range of surveillance receivers.
Demodulator — pulse demodulator module installed in a dedicated slot of the mainframe of a receiver to decode masked signals.
More information is available at the Crypto Museum, a fascinating, virtual museum in The Netherlands.