I was asked to repair or replace an old nurse-call station in a medical room. The current device was discontinued back in the 1980s (Rauland PCS-7351A), but has been working fine until the pull-string was pulled too forcefully. The purpose of the unit is simple: If a patient needs help, pull the string and a switch clicks and turns on a light and buzzer in the nurse station corresponding to the room number of the patient. A light on the switch also illuminates, indicating that it is working.
I took it out of the wall and realized that I had already repaired this unit once before, and it was likely going to break again. So I went online to see if I could find a replacement. I found a variety of call stations from various vendors that said they were equivalent. I finally settled on a suitable model and bought it. I knew the biggest challenge would be getting the back wiring correct. Since nobody who installed the original system had labeled anything, I had to guess at the purpose of some of the wiring.
Happily, the new unit came with a diagram that should give a 1-for-1 idea of where the wires should go. But I noticed a difference in how the old one was wired compared with the diagram. I guessed that it was simply a slight difference and made up my own diagram to take with me to the room.
I hooked it up according to my handwritten diagram and it worked! Happy camper. The new unit is a much simpler toggle design than the old one. Time will tell whether it will withstand use and abuse. The most obvious flaw I saw was the simple nut on the face plate that keeps the switch in place on the new unit. A disturbed patient could unscrew that, push the switch into the cavity and cause a repair call, though the switch would probably still work.
If it turns out to be a problem, I may have to find a smooth surfaced unit to replace it. I did see one such unit in service in the same ward, but haven’t had time to examine the wiring. This is the Rauland PBS113, also discontinued, though we have a spare or two. No idea what the various wires do, and no diagram to help this time. However, an old tech at Rauland kindly sent me a PDF with text that describes which wire goes where on a call station, and that will prove useful.
I did find a waterproof (WP on the diagram) design by Crest that uses a magnetic reed switch. I am guessing at the wiring, and show it here as a possible solution since I haven’t had a chance to try it yet.