Abstract: A delay circuit for use in an electric blasting system including a capacitor for storing electric energy supplied from an electric blaster, an actuation circuit for detecting the stop of voltage supply from the blaster to generate an actuation signal, a circuit for generating clock pulses, a circuit for counting a predetermined number of clock pulses in response to the actuation signal to generate an igniting signal, and a switching circuit for responding to the igniting signal to discharge the electric energy stored in the capacitor through an igniting resistor, the actuation circuit having a zener diode with a threshold voltage. When the voltage supply from the blaster is stopped and the voltage across the zener diode becomes lower than the threshold voltage, the zener diode is cut-off to generate the actuation signal.

Abstract: An electric detonator of the delay type including a housing having a metal portion and an insulating portion, a pair of leg wires extending outside through the housing, a delay circuit connected across the leg wires and generating an ignition current at a predetermined timing, and an igniting resistor connected to an output terminal of the delay circuit and one of the leg wires. In order to check the resistance value of the igniting resistor even after the detonator has been assembled, a by-pass resistor is connected between the other of the leg wires and a junction point between the delay circuit and the igniting resistor. A small measuring current is conducted through the igniting resistor via the by-pass resistor to generate a voltage drop across the igniting resistor. This voltage drop is measured by connecting a voltage measuring device between the leg wire and the metal portion of the housing.

Abstract: An electric detonator of delay type including leg wires connectable to bus wires, a capacitor connected across the leg wires for storing the electric energy supplied from an electric blaster via the leg wires, a delay circuit connected across the leg wires and generating an igniting signal at a predetermined timing, a switching circuit and an igniting resistor connected to the switching circuit, whereby the switching circuit is made conductive in response to the igniting signal to discharge the electric energy stored in the capacitor through the igniting resistor to explode the detonator. In order to operate the detonator reliably and safely, there are provided low and high voltage protection circuits for discharging the electric energy therethrough when the power supply voltage is out of a predetermined normal operation range.

Abstract: A delay type electric detonating primer for use in a multiple-step blasting system including a capacitor for storing electric changes supplied from an electric blaster via bus wires and leg wires, an actuation circuit connected across the capacitor for generating an actuation signal when an energy supply from the electric blaster is stopped, a clock pulse generating circuit having a crystal oscillator and being energized with energy stored in the capacitor to produce clock pulses, a counting circuit which is initiated to count the clock pulses in response to the actuation signal, and generates an ignition signal when the counter has counted the predetermined number of clock pulses, and a switching circuit for discharging electric charges stored in the capacitor through an igniting resistor in response to the ignition signal.