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It has to do with the semiconductor properties and type. There are several families and all have different requirements and advantages or disadvantages. TTL and CMOS are the most common.

Most of these units use TTL (transistor-transistor logic). That is one of the first semiconductor families, fairly rugged & well proven. It's very reliable, capable of providing reasonable power output without additional power components and is relatively inexpensive.

It is designed to work at 5V & do not exceed limits are typically 4.7 to 5.2V. It's very unforgiving once the voltage threshold on either side is approached. Over and it burns up, under and the logic doesn't reliably trigger -- if it triggers at all. The low voltage threshold is the main downside for use on 6V. A poor connection or heavy starter load can easily drop battery below the limit. A few other issues but all in all, the good outweighs the bad for this type application.

CMOS is 12-15V. Very prone to damage by static electricity from careless handling and somewhat noise sensitive. Noise in this reference is electrical garbage on the power supply.

Newer microprocessor logic that use low voltages in the 3.3V range are becoming common but is low power and also very sensitive to handling. Would need more components and possibly even a second power supply to handle higher voltage and current output. The logic is also extremely noise sensitive and needs a lot of additional power supply filtering to ensure a very clean & stable supply voltage.

Howard,

Thanks for the in-depth research @ e-ignition systems and their issues, good and bad. It seems that the good ole reliable points & condenser are hard to beat. There's also the fact that under an electro-magnetic pulse event, the e-ignition systems would fail, whereas the points/condenser would keep on truckin'.

hi ,i LOVE my points eliminator system ,the pertronix guy at the teck line was very helpfull teling me the exact part number ,worked spotlessly ,but they like thier voltage ,one thing that is very helpful is to get a beefy enough battery ,the 6 volt ones these days are less CCHr than whats specified i believe the spec is 1000 ,the 6 volt batteries that you can get now at the battery store are by in large pretty crappy .The pertronix module needs its voltage and they dont work wel if not fed .so a big 6 v forklift battery is the trick ,NAPA (4202 i think)you have to cut the battery tray in 1/2 and put in a piece of metal to make it longer 17 " ,but not wider it took me 1/2 hr for this mod i got better power and no hot start issues after this ,dont forget that old hard unmoving vacumb advance ,this should get swapped out ,its realy easy and could be done at the same time
so my points are in a plastic bag in my cool sliding glove box in case the pertronix thing blows