Switch for self-healing ring

A switch for a self-healing ring comprising:

• a switch having a first stage space division switch, a second stage add-drop switch and a third stage space division switch, each being used for a plurality of nodes;
• clockwise working line and protection line and counterclockwise working line and protection line for reception being connected to inputs of said first stage space division switch;
• and
• four outputs of said third stage space division switch being connected to clockwise working line and protection line and counterclockwise working line and protection line for transmission.

A method of controlling a time divisional switch including a data memory for storing channel data input from a plurality of input lines and a plurality of control memories for storing control information which is used for controlling an output of data from said data memory, said channel data being time multiplexed in time slots, comprising the steps of:

• simultaneously accessing the plurality of said control memories;
• selecting an output from one of said control memories for each time slot and setting the control information obtained from the selected output as a read address for said data memory;
• and
• outputting channel data corresponding to said read address from said memory during the time slot.

A time divisional switch for a self-correcting ring including a plurality of transmission lines comprising:

• a plurality of input lines;
• a data memory storing channel data received by the plurality of input lines, said channel data being multiplexed in a plurality of time slots;
• a plurality of control memories storing control information;
• a read controller simultaneously accessing said plurality of control memories;
• a selector providing an output from one of said control memories for each time slot, the control information obtained from the provided output constituting a read address for said data memory;
• and
• means for outputting a channel data corresponding to said read address from said data memory at a predetermined time slot.