It is more difficult to tell various components by touch
now than it used to be but part of that is due to the different
types of parts now. IC's, for instance have always looked very
similar except for general physical characteristics such as the
case type and number of pins. I can take a certain model of PIC
microcontroller and it would feel just like a NE555 timer chip or
a single 741 op-amp or a Berr-Brown photo op-amp light detector.

	The PIC can be programmed to do a huge number of
different tasks and it still looks the same so one might go about
it to tell people who are blind about the different categories of
parts and show them examples but that's about the best one can
do.

	I've had perfectly sighted people not know what a
particular part is because they don't know what the markings or
colors mean and the part is too small to bare any printing except
what might be read with a microscope or magnifying glass.

	As someone already said, surface-mount parts are
absolutely the worst.

	When describing IC's and transistors, it is good to dwell
a little on basing which means determining which pin is which. A
lot of TO5 transistors, for instance, have a little tab not much
bigger than a Braille dot next to the collector and if you are
looking at the bottom or under side of the transistor, one counts
counter clockwise so it's collector, Base, Emitter. Other case
styles have their conventions, also and that is useful to know if
building or repairing a device.

	IC's work a lot better if you plug them in facing the
right direction. They tend to let out all their magic smoke if
you hook them up backwards.

	The end with the little notch in it is usually the end
containing Pin 1. If it is a duel-enline style, the pin opposite
from 1 is whatever the highest number is such as 16 or 8.

	I've run across some of those duel-enline IC's, though,
that don't have the notch but have the tiniest of pin holes just
above Pin 1. I can feel it if I use the edge of my fingernail but
not the tip of my finger. I have let the smoke out of a few of
those.

Martin