Abstract: A magnetic sensor arrangement for monitoring movement of a vehicle on a path includes a three-axis accelerometer (1) and a processing circuit (2) for evaluating the vector product Hp of magnetic field vectors measured by the accelerometer when the vehicle is at two successive positions on the path. The vector product is utilized to evaluate a parameter related to vehicle trajectory. The arrangement may be used to generate a firing signal in an explosive mine or for monitoring a flow of vehicles along the path.

Abstract: A clock circuit is initiated by an external trigger pulse. Timing measurements commence at a first rate, and after a first delay (t.sub.1) which is sufficient to allow an oscillator of the clock circuit to stabilize. After a second delay (t.sub.1) the clock circuit operates at a second rate which is half the first rate. The clock circuit then represents the time from reception of the external trigger pulse. The first and second delays are derived by charging a capacitor at a constant rate and comparing the voltage level developed across it with respective reference voltages (V.sub.1, V.sub.2) in comparators.In general, the second rate may be 1/r+1 times the first rate, where r is the ratio of the first delay to the second delay.