Northern Telecom Limited

Dieter H Hundrieser

Harold J Ostapovitch

Edward J Olszewski

A fusible link for an electrical circuit consists of a length of fusible material which closely fits an aperture through a ceramic printed circuit board. Ends of the fusible element electrically contact respective electrical leads on opposed surfaces of the board. A resistive film forming part of the electrical circuit is located close to the fusible link site so that when overvoltage conditions exist the resistive film heats the circuit board until eventually the fusible material melts, flows out of the aperture and the electrical circuit is broken. The fusible link is soldered and/or swaged into position and projects beyond the surface of the circuit board so that when the solder melts, surface tension forces tend to pull the solder out of the aperture.

Fusible link

A manual cutover apparatus activates a plurality of circuit boards in an equipment frame in a telephone switching facility. Each circuit board is provided with a manually operable switch for inhibiting the function of the circuit or disabling a line termination at the circuit board, while the switch is in contact with an elongated control member. The control member spans the board locations in the frame and is held in place by slots in a connector shroud at each board position. When the frame is empty of circuit boards, the control member is inserted into slots in the equipment frame. After the required circuit boards are placed in the frame, these boards are activated by the withdrawal of the control member through a hole in a frame member at one end of the frame. The switch includes a base with a pair of terminals and a cantilever spring switch member extending over a groove in the base. As the circuit board is inserted into the frame the control member is received in the groove, displacing the switch member and effecting switching between the terminals.

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Manotick, Canada

Dieter H Hundrieser