Abstract: A vehicle detector includes one or more inductive sensors connected to an oscillator circuit. A timing circuit defines a plurality of sequential measurement frame segments. The oscillator circuit is coupled to an inductive sensor during each of the measurement frame segments. The time duration of each of the plurality of measurement frame segments is measured. After the completion of each frame segment for a particular inductive sensor, a total measurement frame time duration for that sensor is calculated based upon durations of a predetermined number of measurement frame segments for that sensor. The total measurement frame time duration and a reference time duration are compared and a difference is determined. If the difference between the total measurement frame time duration and the reference time duration exceeds a threshold value, an output signal indicative of the presence of a vehicle in the vicinity of the inductive sensor is generated.

Abstract: A method of establishing communication between a first device (e.g. 12) in a first one (e.g. 22) of a plurality of groups (22, 32, 42 and 48) with a second device (e.g. 28) which is a selected one of a plurality of devices (e.g. 24, 26, and 28) and a second one (e.g. 32) of the plurality of groups (22, 32, 42 and 48). The method is utilizable in a communications system having a plurality of groups (22, 32, 42 and 48) and a plurality of devices (e.g. 24, 26 and 28) within at least one (e.g. 32) of the plurality of groups (22, 32, 42 and 48), where communication between the plurality of groups (22, 32, 42 and 48) is by a randomly addressable switching system (20), where each of the plurality of groups (22, 32, 42 and 48) has a unique address within the randomly addressable switching system (20), where each of the plurality of devices (e.g. 24, 26 and 28) within each of the plurality of groups (22, 32, 42 and 48) has a unique identification code within the dedicated line (18, 30, 40 and 46).