37807 A Radio Engineer Checking Amplifiers.
These are line amplifiers, used to amplify different programs from studios and from other parts of the country.
Amplifiers take very weak audio-frequency signals, like those from a mocrophone (see Slide or Stereograph No. 10) or a pickup (see Slide or Stereograph No. 9), and make them louder, so that they can be sent over wires to radio stations all over the country.
Each shelf here is an amplifier. The cans on the shelves have condensers, transformers, and other parts in them. The wires are all bunched together into cables to keep them neat and in order.
This man is checking an alarm circuit. Alarm circuits tell when there is something wrong with the amplifiers. Then the engineer can fix it before it causes a program to be interrupted.
Radio engineers must know a great deal about electricity and electronics, so that they can keep the programs going out on the air all the time.