AUTOMATIC THRESHOLD LEVEL CONTROL SYSTEM

PURPOSE:To stabilizing reading operation for input signals of respective channels by setting an optimum threshold level for each channel even when the length of a bus is long. CONSTITUTION:Automatic threshold control circuits 1 - (m) are provided corresponding to the 1st - (m)th channels. Each control circuit has the same constitution of the 1st comparator 11, the 2nd comparator 12, the 1st AND gate 13, the 2nd AND gate 14, and a control circuit 15. The circuits 1 - (m) set optimum threshold levels for the respective channels with gate signals B1 GATE, B2GATE...EmGATE of the respective channels. A control circuit 25 selects an optimum threshold level and data B2 is read out by the 2nd compara tor 24 with the 2nd selected threshold levels T2.1, T2.2...T2.n, passed through an AND gate 24, and outputted as B2DATA from an output terminal 27.