car call not latching on U.S 1220 : LUSENET : Elevator Problem Discussion : One Thread

Car call not latching. Changed the input buffer and multiplex transceiver. Swapped A3 board. Ohmed TV to A2 connections and all connections on cartop controller board.Suspect A2 board, but want to be sure before I pull all the chips. Also, what is the exact function of the multiplex transceiver? Any old timers out there!!

-- mack (, February 24, 2004


One car call, or all the car calls? Does the car still go to the floors?

Can't remember for sure without looking at the prints, but I think I remember the multiplex receiver just more or less scanning banks of IO, for instance bank 1 might be 1-8, bank 2 9-16 etc. Don't take this as 100 % sure, look at the prints. Multiplexing can also be taking a certain amount of inputs (or outputs) and converting them into binary on 4 wires, etc.

Hope this helps Dan

-- Dan (, February 25, 2004.

It's been awhile but I believe the multiplex is the parallel communication link to the top of car boards. Now most stuff is serial link. You could have a bad output board on the cartop. Also did you try just switching the A3 and A4 board with each other? Goodluck

-- b (, March 10, 2004.

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