US 5,289,044 AGranted

Electronic system switchable between its primary circuit and standby circuit

AssigneeFujitsu Limited

InventorHiroyuki Iwaki

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Abstract

A switching system of the present invention is formed of two identical units. e.g. printed circuit board, the primary and the backup units W & P. Each unit has a switching circuit 1 such that upon receiving a first alarm signal generated due to a malfunction taking place in a main circuit 6(W) of the primary unit W, the switching circuit 1W of the primary unit transmits a second alarm signal S.sub.4 (W) to switching circuit 1P of the standby unit P, then the switching circuit 1P of the standby circuit 1P enables an output of main circuit 6(P) on the standby unit as well as transmits a control signal S.sub.9 (P) to disable an output of main circuit 6(W) of the primary unit. A plurality of the units may form a group so that two groups are in the relation of the primary and the backup. A first unit in the group collects the alarm in the own group and communicates with the first unit of the other group, so that the switching are carried out by the whole group. The switching circuit 1 may be further provided with a manual switching circuit, a switch-upon-extraction circuit which detects an extraction of the printed circuit board from the upper system, and/or a compulsive switching circuit.

A switching system comprising a first unit and a second standby unit, each unit having a main circuit (6), said main circuit outputting a first alarm signal when a malfunction takes place in said main circuit;

a first one (6(W)) of said main circuits being in operation and a second one (6(P)) of said main circuits as a standby circuit to support said first main circuit (6(W)), circuit configuration of said two units being substantially identical to each other, the switching system further comprising:
a first switching circuit (1(W)) of the first unit, having a first alarm detection circuit, coupled to said first main circuit, for receiving said first alarm signal and for transmitting a second alarm signal (S.sub.4 W) to a second switching circuit (1(P)) of the second standby unit (P) upon receiving the first alarm signal from said first main circuit (6(W)), said first switching circuit also having a first switching control circuit, coupled to said first alarm detection circuit and to a first selecting circuit, said first selecting circuit being coupled to a first buffer circuit that is serially coupled to an output from the first main circuit, said first switching control circuit being adapted for actuating said first selecting circuit to enable said first buffer circuit to pass said output in response to receiving an alarm signal from said second switching circuit,
said second switching circuit (1(P)) of the second standby unit (P) having a second alarm detection circuit, coupled to said second main circuit, for receiving said second alarm signal and a third alarm signal from said second main circuit, said second switching circuit also having means for selecting the second main circuit (6(P)) of the second standby unit, said second switching circuit (1(P)) of the standby unit further having means for transmitting a control signal S.sub.9 (P)) to disable said first buffer circuit of the first unit in response to receiving said second alarm signal.

Abstract

Claims7