...it could be early 40's. Was Gates in business then?
Yes.
I have a Gates broadcast limiter, a rack-panel job with black wrinkle finish, that was made in late 30's or early 40's, definitely pre-WW2. It was given to me by a station engineer back in the early 70s'.
It uses an interesting form of compression, employing the thermal characteristics of incandescent pilot lamps wired in a resistive bridge circuit. It also has a stage of standard a.g.c. type limiting. The active stages are push-pull throughout. The sparse literature I have with it claims that it will increase the effective power of a broadcast station by "3 dB's".
But the Gates engineers got it backwards. The a.g.c. limiting stage
precedes the light bulb bridge.
The bulb circuit is useful for maintaining the average audio to a certain level, but it inherently has a slow attack and release time. The a.g.c. circuit can be set to a fast attack time to limit peaks.
Gates should have designed it so that the bulb circuit averaged out the audio level first, and then fed it to the a.g.c. stage to chop off any excessive peaks.
This unit has four high quality push-pull audio input and output transformers, and I have often been tempted to part it out to salvage those transformers, but it is probably a rare historic piece, so I have left it intact. I tried it out once, but it had considerable distortion. Re-conditioning it is on my one-of-these-days list.
