Colorful Wiring for a Model 500 P "Mushroom"
Is'nt there something missing? The hookswitch?
It's pretty obvious that Kenny was trying to depict the removable components: dial, handset, and ringer. On a 425-B network, the hookswitch wiring is soldered into place and can't be removed; the C terminal is solder-only, no screw (and isn't depicted in Kenny's diagram). On a 425-E network, C is a screw terminal but the hookswitch is riveted to the base so it's moot.
Kenny, that's an excellent diagram including good depictions of striped wires such (the red/slate on the ringer); what software are you using to do those diagrams? (And what operating system does it run under; I have "all three" so it's just a matter of which computer to use.)
Agreed, but on a P/U, the positioning of two of the switch wires on the terminal board is critical information.
This is for a P but it could also be for a U if anyone could PM me where the switch wires went.
Thanks,
Kenny C.
Kenny:
I think there is something missing in the schematic. I don't see how the bulb come light up without an extra wire (4 and E1) on the terminal strip.
Thats what I was referring to. I believe the switchhook is what controls the light.
It is. There's an extra set of switches in the pileup that controls the lights in both the P and the U. Those switches add two conductors to the strip. The U also has a key, of course, which introduces yet another pair of conductors to the mix.
The details can be found in the BSPs.
Go to the TCI Library and search for 500P, then search for 500U.
You know, I never realized that the 500P and the 500U have an extra set of switch hook contacts. (This is confirmed in the 500P and 500U BSPs).
I consider that strange, because that's a switch hook configuration found in no other 500 set, and they didn't use that switch hook configuration in the 500 L/M, which is wired for A-Lead control, basically by reusing one of the contacts in the switch hook normally used to switch the Tip and Ring (leaving only 1 lead switched, which is sufficient, of course, to put the phone on-hook).
Why didn't WE use the enhanced switch hook of the 500P and the 500U in the 500 L/M? Or, why didn't they design the 500P and the 500U like the 500 L/M, simply reusing one the contacts in the switch hook normally used for the Tip and Ring?
Is it possible the enhanced switch hook of the 500P and 500U was more expensive and/or lead to unforeseen problems in use and this lead to the early demise of the 500P and the 500U?
The history of the 500 H, P and U sets is summarized in "Dialing in the Dark" (Singing Wires, August 2009).
A key consideration causing the creation of the 500P was: "Due to its wiring arrangement, the 500H cannot be used as tip party on message rate, automatic ticketing, automatic message accounting or zone restriction services. (BSP C32.535, Issue 4, May 1954)"
It would be worth checking to see whether the 500M switch is like the 500H or 500P switch.