This shows Ken Little hitting the master key on the amplifier panel that allowed him to send a signal over all the joker circuits at once.

 

Here are the two dispatching positions at the main panel with a microphone on each side. The master key is seen lower center. The little switches next to it allowed us to cut out certain circuits when transmitting. This was done when repeating certain signals we received from individual companies like out of service. All the switches between the microphones opened the circuit to each firehouse.  They were color coded. The black were single engine houses, red were single truck houses, and olive green were houses with both an engine and truck. We could open and talk to any number of houses at a time. On the right side we threw the switches up and on the left side we threw them down. That way both positions could be in use at the same time. The row of switches above the black area was to activate the simulcast where we could speak to every firehouse citywide or north side only. Above that a panel with counters and meters to monitor output. Above that were speakers including the Englewood talker circuit as well as a direct intercom with the same type of console at Englewood, simple, effective, efficient. 

This image shows the satellite amplifier panel. This was extra and not used much It  operated the same way but had telephone style handsets rather than microphones. The yellow switches along the bottom were to allow us to use individual talker circuits. We would use this to send announcements to small groups for water shutdowns and the like. If you look closely you can see another master key to the right. The gray box above was a register to print out what was transmitted on the striking keys.