Abstract: An upgrade method and apparatus for both remote and key-operated two-step vehicle security systems is disclosed. The upgrade blocks attempts to disarm the alarm circuit when the vehicle is armed and unlocked improperly.The upgrade can be added to existing systems regardless of the polarity of the signals used therein. Improved power-up and remote control features can also be added as a part of the upgrade.

Abstract: An add-on, or after-market, remote-control vehicle security system expander allows auxiliary remote-control functions to be added to previously-installed remote-control systems. Using complementary remote control functions for multiple actuation encoding permits auxiliary function codes to be transmitted without a change of state in the underlying function. Signal validation by coincidence timing and voltage comparison are used to prevent inadvertent local actuation of the auxiliary remote-control functions. Decoding is also limited to a time-window to reduce electrical interference.

Abstract: An easy-to-install automotive security system mounts a siren assembly in the engine compartment and a sensor assembly in the passenger compartment. The assemblies are in wireless, radio frequency communication, thereby eliminating wires extending between the compartments.