ATM Electronics query

["James Dick" <bortech@OntheNet.com.au>]

Hi all

Has anyone built the dc switching circuit shown in Texerau (page 380 of the
second edition.)

I've just copied the artwork and something just doesn't seem right. The
artwork seems to have 12V applied directly to emitters of the TIP31s  while
the schematic shows it should be the TIP32s. I suspect it is just an error
in the copy.

Also i've built a pulse width modulation circuit (Dick Smith kit - in USA
read Radio Shack here) that i was going to run through this switching
circuit. I a real newby to electronics and can anyone see any problem with
doing this. I'm going to build a prototype and try it but if there is any
glaring problems it may save me the cost of the transistors etc.

Alternatively does anyone have any ideas of resources for polarity
switching circvuits on the net ?

Thanx for any info

Mark Bolton