Actually, I've found that, after you learn the basics of boolean logic (and / or / invert) and play around with some of the basic TTL or CMOS Ic's implementing those logic elements, one of the best places to get "instruction" was to look through the "application notes" put out by the various IC manufacturers. Unfortunately, today's ICs are so complex, that application notes are little more than "how to wire the super-whiz-bang-thingy to a 8051 or pentium" so they aren't much good for learning. Check your local used book stores for old data books - I see them all the time around here - but we are in a college town... The application notes are sometimes in the back of these books and sometimes printed as separate volumes. Unfortunately (or perhaps fortunately) those are collectable, too... When I started to design my own stuff, one of the first things I found essential was an oscilloscope. A good used, relatively inexpensive, Tek or HP dual-trace, triggered-sweep, 60 MHz (or so) scope will cost you around 100 to 200 US dollars. I even purchased a Tek 453 on eBay (or is that eOverPay?) for about $150 and it was in near perfect condition. If you don't mind "bulky" and can make it to a "ham fair" or "radio rally", look for some of the older Tek "boat anchors" such as the 535 or 545 or the newer, lighter 56x series (early to mid 60s.) They usually run somewhere around 20 to 50 US dollars over here. They are slower (10 to 30 MHz is common) but that may not be important for learning or restoring old "classics." Unfortunately, these "classics" are quite heavy, so long-distance shipment usually increases the cost beyond their value. I used a 535 (and later a 545) to help keep an old home-brew computer running at Oregon State (many years ago.) The basic machine clock was around 22 MHz (seems fast for 1971, doesn't it?) but it was a "serial" machine so it really had only a 100 micro-second word time. In any case, a scope is SO MUCH better than a logic probe. But speaking of logic probes... Although not a "boat anchor" or "classic", Radio Shack had (do they still sell them?) a little "logic probe oscilloscope" for about 100 US$. Cute little thing had a 20 by 30 pixel (approximate) screen built in to a hand-help box about the size of a normal logic probe. Basically it was a 5 MHz triggered-sweep storage scope. Comes with a cable and software to plug into a IBM compatible for a "real" display. Best "logic probe" I ever purchased. But I still prefer to use "classic" scopes to work on "classic" computers... Gary At 03:14 PM 10/3/98 -0700, you wrote:

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