IBM introduced their clock system with synchronous secondary movements in 1949. In 1955, 12-hour correction was added; the new movements were marked with a “12 HOUR” stamp on the dustcover sticker. In USA, Simplex Time Recorder Company bought the International Time Recorder (ITR) division of IBM in 1958. (It would be best not to quote the years in this summary; corrections requested.) Simplex then began using the IBM design as their primary synchronous secondary movement (rather than their original dual-motor design, which did continue production in other countries where Simplex and ITR remained separate entities).
The IBM design with 12-hour correction became the American “industry-standard” synchronous secondary movement, used in clocks made by most companies in this field, and is under current production by Hansen/Synchron.
If you want to know more about IBM and Simplex clocks in general, I highly recommend the NAWCC forum. Specifically, you can start with the Manuals for Simplex clocks thread/post, which contains a downloadable pdf that will teach you more than you ever wanted to know about how these synchronous secondary movements work (but stops short of adjustment and maintenance, unfortunately).
Being the most common type of synchronous secondary movement, there exists plenty of information elsewhere that I will not duplicate too much (there is even a Wikipedia page about these!).
The Simplex clocks currently 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 may come up with other examples from other places, someday.))
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 movement parts 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 half-and-half 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 as there were two pair of dial designs, there were also different schematic labels (glossy plastic ones and plain paper ones, same information) and slightly-different clutch-magnets that matched for each pair.
Apparently, this system was scrapped because the local Simplex branch office closed (circa-2005) and the college couldn’t get anyone to fix the clocks. It also appears that someone replaced either the motor or the movement in the particular clock shown in January 1998. A factory-installed movement (or drive motor) only lasted less than seven years? That might be part of the problem too…
I strongly dislike this clock—or, this style, that is. Firstly, I can barely read this dial at ten feet away. Secondly, putting the chapter ring inside the numbers is not a license to put 10-inch hands on a 12-inch dial—proper aesthetics dictates that the minute and second hands should still almost reach the outside rim, in my opinion. Unfortunately, it seems that other companies in this business copied the design, making it the contemporary “industry-standard” 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 seven-year-old movement—it’s no wonder that nobody respects traditional clock systems anymore. (End of rant.)
This also shows the proper configuration of a Simplex 6310-8015 electronic secondary, as these originally are (parts not necessarily original to this particular clock; two different movements are shown in these pictures). A movement is also shown from various angles and disassembled. I won’t spend much time on this, as the diagrams in that above-linked document are quite accurate and descriptive.
These four newer clocks originally operated in an electronic (carrier-frequency correction) system, which was driven by a transistorized transmitter (housed in a small cabinet next to the main power distribution panel). As with the different dials and different labels, each pair also had a different but equivalent model of receiver; a pair of model 562-295N and a pair of 562-295P receivers, all tuned to 7020Hz, are shown. This is a higher frequency than the apparently normal 3510Hz; it would be interesting to know why this system used a different frequency.
According to that above-linked document, the electronic version uses DC clutch-magnets and sync-wired uses AC clutch-magnets (that document calls it a “correction solenoid” but the dustcover diagrams call it a “clutch magnet”; to me, a solenoid is a coil or electromagnet that has a moving part, so I choose to use the latter term in reference to these coils). 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 clutch-magnet coils used in the newer solid-state version does, in fact, work with 120vac (despite being a DC coil; the resistance is about 2.2Meg-ohms, by the way). Knowing what I know now, if I were going to use these magnet coils, I would provide a bridge-rectifier for the supply.
((And, by the way, if you think you’re the only one that would like to have one of those big mechanical generator cabinets used in the older electronic systems, I’ll tell you that you are not alone.))
This one is exactly like #19. I ended up with one bad drive motor out of four clocks, so I have yet to use this case.
The only actual bell in my system is a Simplex model 4017-42 vibrating bell (4-inch, 120vac, 11-70) that happens to be painted fire-alarm-red. (Bell is from a different source than above clocks.) It is wired for general signaling, but I usually leave it disconnected as it is way too loud for residential use, in my opinion—unless my intention is to wake up the people across the road.
As expected, here is a Simplex movement and a GRC movement side-by-side. I will now repeat a thought I had when I first popped the cover off of one of those Simplex clocks: “those things sure are tiny” (unnecessary expletives deleted). I was always a bit afraid of Simplex movements—because I can’t get my fingers into them—and I will admit to having those four clocks for almost five years without ever taking a movement completely apart.