National Schools Mechanical Camera
A 1936 publication from the National Schools in Los Angeles describes the camera they used for training their students in television technology. The camera is a Western Junior:
The monitor contains a Western 45 line disk:
Here is a schematic diagram of the camera. Apparently four photocells were used.
The brochure describes a transmitter operating at 2800 kHz. The audio signal is modulated on a 45 kHz carrier, and the video and audio signals are then used to modulate a transmitter. Though a block diagram of the system and a schematic diagram of the transmitter are in the brochure, there are no photographs of the transmitter. There is also a list of licensed TV stations in the brochure, and there is no station shown licensed to National Schools. Probably the National Schools system was entirely closed circuit.
It should be noted that Los Angeles used 50 Hz power at that time.