*http://www.youtube.com/watch?v=EJlgik3ho48 Testing The 74LS138 Decoder
*http://www.datasheetarchive.com/UA556PC-datasheet.html 556 Timer Datasheet
*http://www.datasheetdir.com/74HC164+Shift-registers 74HCT164 8-bit Serial-in, Parallel-out Shift Register
+*http://www.datasheetcatalog.com/datasheets_pdf/D/M/7/4/DM7445N.shtml DM7445 BCD to Decimal Decodersō¸°‡Drivers
* http://chung.yikes.com/~leonard/mirrors/ti99/9900story.html