Abstract: A method and apparatus for use in transmitting information on a wired-OR signal line is described which employs a data transfer protocol exploiting the generally shorter signal settling time occurring following high to low signal voltage transitions than occurs following low to high signal voltage transitions. In accordance with the protocol, the transmission of meaningful information on multiple-driver signal lines is restricted to the assertion of high to low signal voltage transitions. By asserting meaningful information only on high to low transitions, the clock period for the bus may be set based on the voltage settling time resulting from only high to low transitions rather than from arbitrary transitions. As a result, the transmission of meaningful signals are all within the limits of incident wave switching and a high overall information transmission rate is achieved.

Abstract: An apparatus for detecting metallic objects of a predetermined type buried in the ground and distinguishing such predetermined objects from distributed mineral material and undesired objects. An oscillator produces a transmit signal which causes a transmit coil to generate a varying magnetic field. A receive coil coupled with the transmit coil produces a receive signal induced by the transmit signal and having components thereof corresponding to field-distorting materials in proximity to the coil. A multiple sampling circuit produces samples of the receive signal at selected times having predetermined relationships with typical characteristics receive signal components. The samples are analyzed to produce a sense signal representative of the proximity of a metallic object, and a discriminate signal representative of the type of metallic object as well as its proximity.