| 摘要 |
The system employs a sliding tone FM signal to command a remote device such as a balloon; for example, to fire a squib for balloon release. The tone is a slowly-changing, progressively-increasing signal received and detected by discriminator circuitry for application to a phase-locked loop circuit. Comparison of the loop output with a reference voltage provides a release signal when the reference voltage is exceeded. Since the reference voltage is determined by the loop voltage produced by a predetermined command tone, the generation of the release signal is dependent upon the presence of that particular command frequency. A unijunction transistor and an SCR then function as a relay to close a battery-squib circuit. The slowly-changing, sliding tone, as well as the time constant of the phase locked loop circuit, provide a high degree of security from accidental commands and also permit a wide variation in component tolerance including temperature tolerance. Simplicity and low cost permit the receiver to be considered expendable.
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