http://www.reno-auto.net/wp/archives/6582

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Note added at 11分 (2012-12-08 04:05:18 GMT)
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http://www.esr.co.uk/manuals/k2543.pdf

Transistor ignition
A form of ignition system which uses transistors and a special coil. The conventional distributor and point setup is used, but the points merely serve to trigger a transistor which switches the heavy primary current. With the transistor unit, the voltage remains constant, thus permitting high engine rpm without resultant engine miss. Transistors are much more efficient switches at high engine speeds and in addition they don't burn, pit or change gap spacing. The advantages of these systems include greatly increased point life, generally better starting because of improved contact condition and voltage output not greatly affected by Breaker pointDwell time which results in better high-rpm performance. Also point life is greatly extended as the transistor system passes a very small amount of current through the points.
http://www.motorera.com/dictionary/TR.HTM