Postwar American Television
Sentinel Remote Control
This wired remote, made in the late 40s or early 50s, controlled the channel, fine tuning, volume and brightness. The operation of the brightness and volume controls are straightforward, but the channel selection and fine tuning are not. The tuning switch has one common (wiper) and 4 outputs. Here is the code that is developed by the switch:
From our request for ideas on how the remote control works, Tom Genova searched the patent number and discovered how the channel selection works. Here is a description from Arthur Aaron:
In the television there is a motor driven 12-channel turret tuner which also drives four 12-position wafer switches. Each of the 12 poles of the switch array corresponds to a channel position and each of the switches serves one of the four wires. The key to understanding the system is to realize that it is wired in reverse, i.e. the switch positions that correspond to 1 on the control switch are open and the switch positions which correspond to 0 on the control switch are closed. All outputs from the closed switches are paralleled and run to the motor. This means that the motor will run until it encounters the one combination where none of the closed switches of the tuner array is being powered by the sender switch, at which point the tuner motor stops. Clever binary code design.
Several people suggested that a reactance tube, controlled by the potentiometer in the remote control was used to change the frequency of the local oscillator.
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