CSD_logic_probe bill of materials (BOM)
Step #2: Floating tip / tri-state input detection

https://digsys.upc.edu/csd/P01/Logic_Probe/Logic_probe.html


"DY1", yellow LED 5.0mm, biased at 10 mA
"RY1","270 Ohm"
"RT1", "10k"
"DT1,DT2","1N4148", small-signal fast switching diodes