Have to say I am stumped by these inlets - they are like none I have seen before. Several manufacturers did offer locking-type inlets, though I am surprised to see them in a home (they were usually for public buildings, schools, etc).
How many inlets do you have in your home? There were usually fewer than would be installed today in a home of a given size, and the hoses were made longer to compensate. 35 to 50 feet was common in the early 1900s, and the hose would have been made of canvas and rubber with a wire spiral inside.
One clue as to brand would be the inside diameter of the pipe and the wall inlets. "Low vacuum/high volume" centrifugal fan machines (TUEC, Invincible, Sturtevant, Spencer) used 1.5" or larger inlets, and 2" or larger pipe lines (usually max 2.5" in a home, even a large one). "High vacuum/low volume" positive displacement pump units (Arco Wand, Richmond, Thurman, plus the original "Vacuum Cleaner Company" of New York among others) had wall inlets with an ID closer to 1" and piping of typically 1.5" (larger for main lines of multi user systems, but these wouldn't be found in a residence).
As far as adapting a modern system to make use of the piping and inlets in your home, the suggestion above to hook a vacuum like a "shop vac" to the pipe in the basement, to check that suction reaches all the inlets, is a good one. Also examine the gaskets inside each inlet flap. 109 year old rubber will probably have to be replaced in order to get them to seal, otherwise the system performance will be reduced due to leakage. A little experimenting will be in order to adapt a modern central vacuum hose (whose end cuff is 1.5" OD) to whatever inlet size you may have (smaller or larger - for example, a 1.5" ID hose cuff is about 1.8" OD which fits the Spencer and TUEC inlets pretty well, and 1" copper pipe is about 1.125" OD which fits Arco Wand inlets). Unless switches are present above each inlet and the wiring is still intact, you will probably want an RF wireless hose handle to activate the system, which is typically used for retractable hose installations today.
Adapting the pipe size to the new machine should be no problem. Just take care to chamfer the inside edges of the old and new pipes where they join to give a smooth transition to prevent blockages. A rubber "Fernco" coupling will probably be the thing to use. The pipe/inlet size should also affect the type of machine you install. A small diameter system should receive a unit with more waterlift, while a large diameter system should get a machine with more CFM. This will help to optimize the performance of the system.
One last question - I know you said the motor has been removed (sadly) but the "diaphragm" is still present. Not sure what that would be, but I would be grateful for a picture!
Hope this info is helpful. It would be really cool to get your system working again! Wonder how long it's been since those old pipes had any air or dirt moving through them.
-Owen
