Security System


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Key-release Security System - Despatcher Console
Key-release Security System - On-Site Key-Keeper

Theta Engineering did the circuit design, circuit board artwork design and the low-level firmware development for a new generation of the Knox Sentralok key release system. This project utilized three firmware developers and an electronics engineer. Numerous technologies were involved:

  • C code development on the MSP430 microcontroller
  • 10-year lithium-powered real-time clock implemented using the MSP430 and taking advantage of its low-power features and dual-crystal capability (one high-speed crystal for normal operation and one 32KHz watch crystal for time keeping).
  • MSK Modem. MSK stands for "Minimum Shift Keying". It is a form of audio modulation optimized for data transmission over analog radios.
  • DTMF detection and transmission. "Dual Tone Multi-Frequency" signaling is what you hear every time you dial a touch-tone phone.
  • Infrared communications using IrDA-type transmitters and receivers
  • Serial flash memory
  • Security and encryption through the use of Dallas Semiconductor's SHA-1(Secure Hash Standard) devices
  • LCD/keypad/beeper user interface
  • RS-232 communications