Coin validation apparatus
First Claim
1. A method of validating a coin comprising providing only a single feedback oscillator having a tuned electrical coil permanently connected in its feedback loop, positioning a coin adjacent said electrical coil, operating said single feedback oscillator and monitoring its frequency, selectively including a phase shifting network in said feedback loop of said single feedback oscillator, operating said single feedback oscillator and monitoring its frequency when said phase shifting network is included in its feedback loop, deriving from said monitored frequencies two parameter signals characteristic of the effect of said coin on the inductance and loss factor of said coil, and comparing said two parameter signals with reference values to determine if said coin is valid.
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Accused Products
Abstract
Coin validation apparatus may be associated with a coin freed mechanism on coin receiving machines or form part of a coin sorting apparatus to check that coins are valid coins and not counterfeit. Recently, it has become particularly convenient to use the interaction between a coin and an alternating magnetic field to gauge various parameters of the coin thereby to determine if the coin is valid. In such a method the frequency of a feedback oscillator having a tuned electrical coil in its feedback loop is monitored when a coin is present adjacent the coil, the frequency is then monitored when a phase shift or time delay network is also included in its feedback loop, two parameter signals characteristic of the effect of the coin on both the inductance and the loss factor of the coil, are derived from these maintained frequencies and the two parameter signals are compared with reference values to determine if the coin is valid.
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Citations
13 Claims
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1. A method of validating a coin comprising providing only a single feedback oscillator having a tuned electrical coil permanently connected in its feedback loop, positioning a coin adjacent said electrical coil, operating said single feedback oscillator and monitoring its frequency, selectively including a phase shifting network in said feedback loop of said single feedback oscillator, operating said single feedback oscillator and monitoring its frequency when said phase shifting network is included in its feedback loop, deriving from said monitored frequencies two parameter signals characteristic of the effect of said coin on the inductance and loss factor of said coil, and comparing said two parameter signals with reference values to determine if said coin is valid.
- 2. Coin validation apparatus comprising an electrical coil, means to hold a coin at a fixed reference position adjacent said electrical coil, only a single feedback oscillator including a feedback loop, said electrical coil being permanently connected in said feedback loop of said single feedback oscillator, a phase shifting network switchable into and out of said feedback loop, frequency monitoring means for monitoring the frequency of said single feedback oscillator and for outputting a signal indicative of its frequency, parameter means responsive to said output signal of said frequency monitoring means when said phase shifting network is both switched into and out of said feedback loop for producing two respective parameter signals characteristic of the effect of said coin on both the inductance and loss factor of said coil, and comparison means to compare said two parameter signals with reference values to determine if said coin is valid and to output a coin validation signal when both of said parameter signals correspond to said reference values.
Specification