What is meant by a TR detector?
This designation refers to Transmit/Receive detectors, an older type of detector which is not very popular today. Its main disadvantage is that there is no provision to compensate for the ground effect, other than moving the threshold up and down. Fig. 1 shows the coil arrangement. The receiver coil is mechanically adjusted so that the magnetic field from the transmitter coil is essentially balanced out. For this reason, the detector is also know as the “induction balance” detector. A metal object within the reach of the field of the transmitter coil will unbalance the arrangement–ferrous and non-ferrous metals alike. Mineralization in the ground will unbalance the coil system in the opposite direction, and the detector must be “retuned” so that a metal signal will again exceed the threshold and an audible tone will be produced. Apart from this shortcoming, the detector yields good results, especially on the beach. 9. Q: The threads on the plastic rod that fastens the coil in my metal
