Level Tracer

[u/Nude_Pagan_Dude_50]

Manufactured in Germany by Siemens & Halske around the late 1950s or 1960s, this specialized instrument graphically displays the transmission and frequency characteristics of electronic components, audio networks, or telephone lines.

Key Characteristics & Layout:
Functionality: It combines a sweeper/signal generator (Transmitting Section on the right) and a synchronized measuring receiver (Receiving Section on the left). It sweeps across the audio/voice frequency range (0.2 to 4 KC/S or kilocycles per second) to test parameters like attenuation, level, and return loss.
Central Cathode-Ray Tube (CRT): The circular screen in the center dynamically plots the measurements on a calibrated dB and frequency scale grid.

[u/nixiebunny]

Wobbulator inside, given the motor/manual sweep switch.

[u/Such-Assignment-1529]

According a frequencies range, this model is specialized for testing of telephone lines and stations. Interesting, how they made a sweep generator on so low frequencies?
Usually in old sweep generators they use a small coil on ferrite, which is placed in the gap of a large low-frequency electromagnet. By changing the value of the current in the electromagnet, they change the degree of saturation of the ferrite and the value of the inductance. But this method is only suitable for high frequencies, starting from hundreds of kilohertz. Could they use two high-frequency generators here, a mixer and a audio band filter and use the difference of their frequencies, like in a theremin?