Wilkes-Barre A transponder system for monitoring and logging depository transactions in which bags loaded with funds to be deposited in a bank are put, one at a time, into a bank inlet hopper from which the bags drop through a chute into a vault. Incorporated in each bag is a tag in the form of a passive transponder adapted to receive a radio-frequency interrogation signal and to retransmit the signal as a coded signal defining a number identifying the bag. Installed in the vault is a transceiver that transmits the interrogation signal in a confined radiation field within the vault, the field being intercepted only when a tagged bag falls into the vault or is withdrawn from the vault. When the field is intercepted by a tagged bag, its transponder picks up the interrogation signal and transmits to the transceiver the coded signal identifying the bag. Each coded signal received by the transceiver is conveyed to a digital computer which registers the identity of the tagged bags and the time and date at which each bag is deposited or withdrawn from the vault.
Data collected by the computer is printed out to provide a log of depository transactions.
A transponder has a resonant RLC circuit with one or more electromagnetic energy storage components that vary in response to an externally applied modulating energy field. In addition to the externally modulating energy field, a base station transmits a carrier signal with a frequency essentially the same as the quiescent resonant frequency of the RLC circuit. Effects of the modulation are detected by the base station. This allows the resonant circuit to modulate the carrier signal with multiple modulation frequencies to encode multiple bits of information on the carrier. Shin Alps Electric Co An alarm-equipped electronic article surveillance system which is easy to handle, which provides against the triggering of false alarm, and which reliably surveys articles of interest against theft.