R 4 DC 7 Q 3 GND 1 VCC 8 TR 2 TH 6 CV 5 U1 NE555 CKA 14 Q0 12 CKB 1 Q1 9 Q2 8 Q3 11 R0(1) 2 R0(2) 3 R9(1) 6 R9(2) 7 U2 7490 A 7 QA 13 B 1 QB 12 C 2 QC 11 D 6 QD 10 BI/RBO 4 QE 9 RBI 5 QF 15 LT 3 QG 14 U3 7447 A1 10 S1 9 A2 8 S2 6 A3 3 S3 2 A4 1 S4 15 B1 11 B2 7 B3 4 B4 16 C0 13 C4 14 U4 7483 R8 1k R9 1k D1 LED R10 0R1 C1 0.01u C2 0.01u D2 1N4007 +5v Co