Abstract: An optical bi-directional line switched ring for performing adding and dropping of traffic into the traffic path and for performing ring and/or span protection switching. The optical bi-directional line switched ring include a plurality of nodes, each node having multiple input demultiplexer/output multiplexer sections, a command and control channel having multiple fibers, and up to N-1 slave circuits. Each multiple input demultiplexer/output multiplexer sections has an input demultiplexer to receive and demultiplex signals from a fiber and an output multiplexer to receive the demultiplexed wavelengths from internally and multiplex them into an outgoing signal. The command and control channel can be a standard bi-directional line switch that has one channel coupled to each fiber of the system.

Abstract: A negative, edge-triggered R-S latch, which provides predetermined output states for any and all R-S inputs, may be obtained by using an AND-OR-Invert (A-O-I) circuit in conjunction with a "D"-type flip-flop. The reset input and the Q-output of the flip-flop provide the inputs to one AND-gate of the A-O-I circuit. The set input and Q-output of the flip-flop provide the inputs to the other AND-gate. The output of the A-O-I provides the clock input to the flip-flop. The Q-output is also connected to the D-input of the flip-flop.