This is the Western Electric Equipment Archive Section of
The Broadcast Archive

The building block of the 300 series was the model 23A transmitter. 

They were of the second generation of broadcast products by Western Electric. Economy was the hallmark of this generation of transmitters; intended primarily for the small stations, there were two models produced. 310A was a 100 watt unit and the 310B was the 100 watt unit with additional final tubes to produce 250 watts. These transmitters served small stations and night time powers for many, many years.