[zhrvoj]

I was maintaining instrumentation is similar control rooms. The man behind panel. Petrochemical industry, recorders, indicators, alarms, tranducers, pneum. controllers. Mix of pneumatic and electronic technology (thermionic valves mostly). US technology from 50's/60's and it looked the same like this. Remember Taylor 700T chopper stabilized thermocouple transducer, Honeywell, Fisher instrumentation...

[TedDoesntTalk]

Did you ever work with the Honeywell TDC-3000 ?

[zhrvoj]

No. Honeywell TDC's were in other plants - polyethylene, polystyrene. This was old olefin plant. Not any kind of control logic, no computers, no scada. Just control loops for flow, presssure, temperature on the field - with control room indications, and/or PI/PID controllers in the control room. So we could adjust PID loops from control rooms. And most important - there was man in the middle, and his logic! Later I lead maintenance on steam generation plant, and there we also didn't have any visualization of process, just bunch of logic cards in two racks, cards full of CMOS 4000 IC! I loved it. We searched for logic faults looking at the bad xeroxed paper logic circuit schematics!! Checking inputs from field, and deducing why output is not ok, and some valve not actuating. Changing IC's, or repairing cold junctions. People knowing chemical proccess were crucial!

[zhrvoj]

Can you imagine perfectly stable operational amplifier made with thermionic valves (tubes), ECC81, ECC82, ECC83. Amplifying DC millivolts to stable volts and converting them to pressure 3 - 15 psi, because intrinsic safety circuits were not possible at that time. 4-20mA came later.