Logic Probe

Schematic

Parts List

QTY  PART-REFS           VALUE                                      
---  ---------           -----                                   
Resistors
---------
1    R1                  2M2                                               
3    R2,R3,R5            1K                                                
1    R4                  4M7                                               

Capacitors
----------
1    C1                  100nf                                             

Integrated Circuits
-------------------
1    U1                  4001                                              

Diodes
------
3    D1-D3               LED