Abstract: A unit is located inside a mailbox which prevents access to the mailbox through the door of the mailbox when the unit is in place. The unit includes a fence-like portion that is attached to the mailbox body by an arm that is locked to the mailbox in the rear of the mailbox. The fence-like portion is locked to the arm and is attached to the mailbox by a hinge. When unlocked, the fence can be pivoted out of the way to allow access to inside of the mailbox.

Abstract: A sampling type of metal detector is described in which an oscillator transmits an oscillator signal current through the transmit coil of the detector to produce an electromagnetic field in the region of a search head. A received signal is induced in the receive coil of the detector when a metal object is present within that portion of the electromagnetic field which is external to the search head. A sampling pulse generator produces sampling pulses, at a time related to the output signal of the oscillator, which are transmitted to a sampling circuit for sampling the received signal. In the preferred embodiment, the received signal is sampled at a time controlled by a phase shift adjustment means to produce an output sample voltage such that any indication due to mineral soils or other background conditions is excluded from the sample.