Abstract: A sequential blasting system for use in particular in mining comprises a plurality of detonator stages S1, S2, . . . , each of which contains a series circuit consisting of a thyristor T and a detonator means ZE, said series circuit being interposed between two supply leads A, O; B, 0. The signal voltage for the thyristor T in each stage is derived solely from the switching state of the thyristor T of the preceding stage. This causes activation to be transferred from stage to stage independently of the detonator means ZE, in particular irrespectively of whether or not a detonator has been attached and whether or not this detonator becomes highly resistive or not as it should upon being activated. This eliminates the errors that have occurred in known circuits. Upon firing the blasting system, such errors can cause the detonation to occur not only at the first detonator stage, but simultaneously at a location where a detonator is missing as well.

Abstract: A relay driving circuit for a latch-in type magnetic relay having an excitation coil, generating a set current and a reset current of opposite polarity for the coil. A capacitor is provided between the input terminals of the circuit in series with the coil. A set switch is connected in series with the coil and the capacitor, and a reset switch is connected across the series combination. An input voltage level detector is provided to make the set switch conductive, thereby applying the input voltage to the excitation coil and the capacitor to provide the set current. As the input voltage decreases below the trigger level, the detector makes the reset switch conductive to allow the capacitor to discharge current in the opposite direction through the excitation coil.

Abstract: A contact spring arrangement for an electromagnetic relay includes a contact spring forming at least one movable contact for cooperation with a fixed contact, and an actuator which embraces the contact spring and has a first portion for moving the movable contact towards the fixed contact, thereby closing the contact couple, and a second portion for withdrawing the movable contact from the fixed contact, thereby opening the contact couple. The actuator is so shaped that the distance between the location at which the first actuator portion engages the contact spring and the contacting location of the contact couple is greater than the distance between the location at which the second actuator portion engages the contact spring and the said contacting location.

Abstract: Circuit arrangements for the control of a bistable relay having a capacitor connected in series with its excitation winding, in which the series connection of coil and capacitor is connected to excitation voltage for the excitation of the relay and simultaneous charging of the capacitor, and, upon absence of excitation voltage, is short-circuitable through a semiconductor switch having its output circuit parallel-connected with the series connection of coil and capacitor, whereby the relay switches back to its starting position.