초록 ▼

The invention comprises a low power broadcast system that is applicable especially to the so-called “electronic shelf”for retail stores, wherein the shelf edge carries price displaying modules that can be addressed and controlled from a central computer operated station. The system also permits the

The invention comprises a low power broadcast system that is applicable especially to the so-called “electronic shelf”for retail stores, wherein the shelf edge carries price displaying modules that can be addressed and controlled from a central computer operated station. The system also permits the modules to broadcast back to the central station to confirm safe receipt of data and to give information as to stock levels, etc. A broadcast system avoids the need for wiring so that location changes are facilitated. To overcome the extremely noisy environment and to conserve power consumption, and hence battery life, the system employs a low frequency (132 kHz) reference carrier transmitted by the base station in discrete segmented packages, each of which frames a base data word transmitted by the base station and a corresponding module data word transmitted by the module a fixed period after the end of the base word; the base receiver then has precise time information for receipt of the module word and can “look”for it among the noise. The carrier received by the module is divided and the lower frequency used to demodulate the information-carrying transmission from the base station of the same frequency, avoiding the need for a phase locked loop detector; this lower frequency is also used for the module transmission. The module employs an air-cored loop antenna coil for the lower frequency and a ferrite-cored loop antenna for the higher reference frequency, while the store antenna is segmented for selection of the group of modules to be addressed; the antenna contacts the metal shelving to provide electromagnetic coupling thereto. Each module contains a microprocessor which controls the operation. Each module has “concealed”buttons which can be enabled and used to insert data to be transmitted therefrom. A charging circuit can be used as the power source employing the received RF carrier energy.

대표청구항 ▼

A signal broadcast system comprising a broadcast transmitter and at least one broadcast receiver, the system comprising: means for generating at the transmitter a first carrier of a first reference frequency N and for broadcasting that first carrier; means for generating at the transmitter a second

A signal broadcast system comprising a broadcast transmitter and at least one broadcast receiver, the system comprising: means for generating at the transmitter a first carrier of a first reference frequency N and for broadcasting that first carrier; means for generating at the transmitter a second carrier of second frequency N/n derived from the first reference carrier where the divisor n is greater than 1, for modulating the second carrier with a digital modulating signal in accordance with the digital information to be transmitted thereby, and for broadcasting the digitally modulated second carrier; means at the receiver for receiving the first carrier and for dividing it by the divisor n to produce a corresponding demodulating signal of frequency N/n; and a demodulator at the receiver receiving the second digitally modulated carrier and the demodulating signal and demodulating the second digitally modulated carrier with the second demodulating signal to generate a resulting digital information signal.