My new Technics SL 1500-C has three speeds. You select 78 rpm by holding 33 and 45 buttons together. Some record changers and single play automatics had small buttons in the platter each at 7", 10", and 12". Whichever record size was on it, that's where the tonearm drops. I think new Dual's have electronic sizing depending on the speed chosen.
A British made ADC model had programmable tracks with buttons along the front top and a silver globe module which has the processor. Worth a lot when working but can be a nightmare to service.
Those record changers that used a small button in the platter for size sensing were VM units.
The ones labeled as Zenith and other brands were also made for them by VM.
It was ONE button on the platter, which if pressed down by a 10" record, would trigger the 10" setdown position.
If the button was not pressed, it triggers 7 inch record setdown.
If the button AND the lever near the tonearm was pressed, it triggered the 12" setdown.
I had a nice pristine 1966 Zenith/VM changer with the floating "2G" cartridge sitting around from a TOL portable that I junked years ago.
So... I built a base AND dustcover for it, plus designed an internal preamp-equalizer for using it with modern Aux inputs so it would interface properly.
It's so close to sounding like a decent mag-cartridge turntable.
I put it on CraigsList.
A friend of mine wanted to get into collecting records and begged me to sell it to him. - He fell in love with the styling.
Besides me knowing electronics, I'm also a pretty talented wood-working nerd.
My garage has all the equipment I need to work with wood, and metal.
So here's that "Zenith" custom changer that my friend loves.
