If you really want to know about IBM/Simplex clocks, I highly recommend the NAWCC forum. Specifically, you can start with this thread/post, which contains a downloadable pdf that will teach you more than you ever wanted to know about Simplex synchronous secondary movements.
The Simplex clocks listed below all came from the same place—a certain local community college, the building to which was built in 1991. Unfortunately, they had already abandoned the clock system and thrown out most of it a couple years before I was there.
I have mostly given up trying to use these junky Simplex clocks; but I have to keep the page, because, well… it is the most popular page on this site!
It’s somewhat disappointing that my first and only double-sided clock has to be a Simplex. On the other hand, out of all the dial designs that I have seen on IBM/Simplex synchronous clocks, this has to be the best looking. I especially like the oversized counterweight on the second hand. Too bad the cases are plastic and the movements are junk.
It is interesting to note that this set had one of these dials and one of the other style (as below) when I got it. That configuration may or may not be original, but all the parts were originally installed in the same building. Also, the sticker and dustcover is the same on #18b as this. Just like there were two pair of dial designs, there were also different schematic labels (glossy plastic ones and plain paper ones) and clutch magnets that matched for each pair.
It also appears that someone replaced either the motor or the movement in this particular clock in January 1998. (A factory-installed movement or drive motor only lasted less than 7 years?) It is funny though, because the first time I ran a 12-hour correction on this one, the hands released to some odd time like 9:12.20. Despite someone’s best efforts otherwise, this clock has the best movement out of the group.
I strongly dislike this clock. Not so much this exact clock, just this style. Firstly, I can barely read this dial at 10ft away. Secondly, putting the chapter ring inside the numbers is not a license to put 10-inch hands on a 12-inch dial—in my opinion, proper aesthetics dictates that the minute and second hands should still almost reach the outside rim. Unfortunately, it seems that other companies in this business copied the design. I am of the firm opinion that a lot of people totally dropped the figurative ball with this, overall. If this is all there is to choose from—including the bad 7-year-old movement—it’s no wonder that nobody respects traditional clock systems anymore.
Speaking of crappy movements that are designed to fail, you can almost see my little paper clip and super-glue modification to the correction assembly. That brass (or something softer) gear finally stripped off on the spot where it always skips during the 12-hour correction—as it seems to be designed to do after about 10 years of use. The paper clip stop-bar that I added just allows me to adjust the gear down so it sticks on a slightly different spot. If I am careful with the adjustments, the life of that part should be almost 10 times longer with the paper clip stop-bar.
This one is exactly like #19. I ended up with exactly one bad drive motor out of four clocks. This clock somehow turned into the designated junk pile.
In any event, these clocks just had regular 3-wire synchronous movements with solid-state receivers attached. I have read that the older tube receivers used a 150v clutch magnet (that will not pull-in with mains voltage by itself); but the newer solid-state version does, in fact, use regular 120v coils.
Do I really want any other Simplex clocks? Probably not. It would be neat to have at least one IBM-branded “electronic” synchronous with the older tube receiver. Of course, it would almost make having Simplex clocks worthwhile if I could come up with a transmitter (generator cabinet), but such a thing would likely just be way too much trouble to actually try to use (still be neat to have one, though).
I would be most likely to buy a few Lathem SS-series clocks, on the other hand (or rather, with the same movement), especially if I ever have a larger house-building with an obvious smaller addition—as that would create the type of setup the LTR8-128 was specifically designed to control.