Abstract: In an optical contact unit and an optical connector using the optical contact unit, the optical contact and other components are integrated into a single unit which is collectively mounted and removed to and from the optical contact holding member so that the mounting and the removing operations is facilitated. The optical contact unit comprises an optical fiber with an end portion, a ferrule fitted onto the end portion of the optical fiber, a sleeve containing and supporting the ferrule so that the ferrule is movable in an axial direction thereof, a biasing member contained in the sleeve for biasing the ferrule to make the ferrule project from the sleeve in the axial direction, and a stopper for limiting the movement of the ferrule which is forced by the biasing member to move in the axial direction with respect to the sleeve.

Abstract: An optical connector comprises an optical connection adapter and an optical plug. The optical connection adapter includes a sleeve to be attached to a first circuit board. The optical plug includes an optical contact to be inserted into and removed from the sleeve, and a contact holding member to be attached to a second circuit board. A variation of the optical connector comprises an optical connection adapter and an optical socket. The optical connection adapter comprises a pipe, an optical fiber arranged in the pipe, an optical connector connected to opposite ends of the optical fiber, and a contact holding member which is inserted into the pipe to be movable along the cylindrical axis and which is for holding the optical contact.

Abstract: An optical D flipflop comprising a 2.times.1 optical switch and a optical bistable element. The flipflop has a first input end adapted to receive optical digital data, a second input end adapted to receive a biasing optical signal and at least one output end for emitting a light beam comprising the bias signal or optical information pulses, depending upon the state of a clock signal applied to the signal flip flop switch. The flip flops, when connected in cascade through light branching circuits, act as a shift register.

Abstract: A semiconductor (preferably a thyristor) switch has characteristics that can be represented by an equivalent circuit including an interconnected pair of opposite conductive types of transistors. The base terminals of these transistors represent anode and cathode gate electrodes of the thyristors. An amplifier which is free from erroneous actions due to the impression of a transitional voltage is connected to an electrode of the thyristor, which corresponds to the base terminal of an equivalent transistor of a first conductive type, in order to supply a gate current. A resistor across the base-emitter junction of an equivalent transistor of a second conductive type has a sufficiently low-resistance value to satisfy a predetermined dv/dt-bearing capacity. Therefore, a sustaining gate current is provided responsive to an amplification of the input to the amplifying means.

Abstract: An A.C. signalling transmission trunk circuit has a single-polarity drive voltage source for controlling a pair of thyristor-switching circuits which are assigned, respectively, to a subscriber line pair. The voltage source is arranged to supply either a positive or negative half-wave A.C. signal voltage over one side of the subscriber line to one of the thyristor-switching circuits. Another half-wave A.C. drive voltage of the same polarity (but 180 degrees out of phase) is applied over the other side of the subscriber line to the other of the thyristor-switching circuits. The instantaneous potentials on the two sides of the subscriber lines have single polarity--either a positive or a negative potential--while supplying the A.C. signal to the subscriber set.