Laurens Hammond invented the synchronous electric motor once A/C domestic voltage had proliferated enough as an alternative to the original D/C electrification

Laurens Hammond invented the synchronous electric motor once A/C domestic voltage had proliferated enough as an alternative to the original D/C electrification first established by Edison. This made it possible for the first time to build clocks based on the stable frequency of the incoming A/C supply voltage, much more reliably than those based on the incoming line voltage, which varies quite a bit whether it is A/C or D/C. This put him on the map as a manufacturer when he went forward to build Hammond clocks commercially. Years later his engineers encouraged him to consider developing an electric church organ, which would be possible to remain in tune regardless of variations in line voltage themselves. Hammond was not musically inclined but he did it anyway. Right up there with the Great Men in the most legendary way. http://thehammondorganstory.com/ http://thehammondorganstory.com/ By the time the 1960's came around, almost all new American vehicles were recognized as modern Space Age conveniences, and a factory clock (mechanical analog, naturally) had become almost a universal standard accessory beyond the most budget price points. There were a couple drawbacks to the factory clocks, they had to be connected to the car battery at all times to keep running, they didn't drain the battery very much at all but still would eventually deaden it if undriven, way worse than no clock. And they depended on the incoming voltage which determined the internal clock motor speed to begin with. Different automotive electrical systems and batteries themselves do vary perhaps 10 percent about a nominal design voltage of 12 VDC. There is no stable A/C in the car that a synchronous motor would need to run on[0]. These now-vintage clocks were self-correcting. You correct them yourself. Actually the same twisting of the knob to move the hands of the clock, which was familiar from earlier non-correcting clocks simply did the job. So they were somewhat backward-compatible. Only the Space Age units had smart enough mechanical ability to take into account how much and in which direction you moved the hands, and adjusted the previous running speed accordingly. If the clock was not very close to correct time when you adjusted it, it would take repeated adjustments over a number of days or weeks to get it to very realistic speed. All it really did was successive approximation. You had to supply your own natural intelligence. Even at the time lots of drivers never knew this, and there was widespread disappointment over the wildly inaccurate clocks "which were OK when new but went downhill 'through time'". They only added maybe a dollar to your car payment but that was very expensive compared to a highly reliable cheap household clock at the time. When you think about it, today lots of drivers are not quite up to par when it comes to engaging the amount of natural intelligence that would be needed in many other ways besides timekeeping. [0] The electrical "vibrator" which provided switch-mode 12VAC which could be stepped up by a transformer to supply much higher voltage to power vacuum tube radios still produced a variable A/C voltage & frequency, dependent on the underlying D/C supply voltage.