Electronic alarm apparatus.

摘要

An electronic alarm apparatus for monitoring the presence or absence of objects within a given area, comprising a transmitter including means for attaching same to an object, a shift register (28) for storing a digital identification code, and electronic circuit means including a time delay circuit (50) for periodically transmitting the digital identification code as a radio frequency signal, and further comprising a monitor including a logic timing circuit (70, 72) for activating a receiver (58) for receiving the radio frequency signal, a check circuit (62) for comparing the received signal with a stored identification code and audio logic circuit (78) and liquid crystal display (80) for providing audio and visual indications upon failure of receiving a given number of consecutive transmissions from a given transmitter, the transmitter further including tamper switch (22) and tamper flag logic circuit (52) for changing the digital identification code stored in the shift register (28) upon premature removal of the transmitter from the object.