Apparatus for testing metal detectors

Claim 1

Apparatus for testing the operability of devices having a low-power, low-frequency radio transmitter and a receiver tuned to receive signals from said radio transmitter, comprising: an antenna which is resonant at the frequency of operation of a said device being tested, transmitter means connected to said antenna for supplying a signal at the frequency of operation of a said device being tested for radiation from said antenna, variable power supply means selectively connected to said transmitter for varying the power of the signal produced by said transmitter and radiated from said antenna, receiver means selectively connected to said antenna or to said transmitter for, respectively, providing a voltage output corresponding to the field strength of a signal received by said antenna, or providing a voltage output corresponding to the power of the signal supplied by said transmitter, voltage measuring means for providing an indication of the value of the voltage output from said receiver means, switch means for connecting an input of said receiver means to said antenna and disconnecting said power from and thereby deactivating said transmitter and, alternatively, for connecting the input of said receiver means to a terminal from which the power output of said transmitter can be sensed and connecting the output of said power supply means to said transmitter and, means for receiving and placing a said device to be tested and defining a predetermined, constant distance and orientation of the device to be tested with respect to said antenna to thereby define predetermined, constant field strengths for given transmission levels from the said radio transmitter in said device being tested or said transmitter in said apparatus whereby it can be determined whether said radio transmitter in a said device is producing an output at a predetermined level as it can be determined whether said receiver in a said device is capable of receiving signals at a predetermined level.