This invention relates to an electronic
metal detector having transmit
electronics comprising switching
electronics arranged and adapted to generate a transmit
signal, the transmit
electronics comprising at least two power sources, a first power source and a second power source, the transmit electronics being connected to a transmit coil arranged and adapted to transmit an alternating
magnetic field, wherein the switching electronics are adapted and arranged to switch a first
voltage of the first power source to the transmit coil for at least a first period and also a third period, the switching electronics being adapted and arranged to switch a second
voltage of the second power source to the transmit coil for at least a second period. The switching electronics are further adapted and arranged to switch approximately zero volts to the transmit coil for at least a fourth period, the second
voltage being opposite in polarity to the first voltage, and an
absolute magnitude of the first voltage being at least ten times an
absolute magnitude of the second voltage, the said first voltage, second voltage, first period, second period and third period and fourth period being selected so that a transmit coil current increases in a second polarity sense during the second period and changes sign during the second period, and the transmit coil current increases in an opposite polarity sense to the second polarity sense during the first period and also the third period, receive electronics is adapted and arranged to receive and process a receive
magnetic field during at least some of the second period and fourth period to produce an indicator output, the indicator output at least indicating the presence of at least some
metal targets under the influence of the said alternating
magnetic field and indicating at least a characteristic of the
metal targets.