Thunderbolt Siren
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The Thunderbolt siren uses a fairly elaborate set of electrical controls for operation. Since the Thunderbolt has 3 motors it takes a Federal RCM cabinet with 3 motor starters to operate it. The original controller for the RCM is the the Federal AR or AF timer. See the description of the timers at the bottom of this page

Federal Signal Thunderbolt RCM Controls
Dirty cabinet with ice
This is a Federal Signal RCM1A cabinet which is equipped with 3 motor starters. The 3 green items are the motor starter contacts and the starter activation coils and plungers are just below the contacts. These starters allow switching of the high current to the various siren motors by a lower current switching contol circuit like a big relay. The RCM1A is used with the Thunderbolt siren when the siren is operated from a 3 phase power source. The RCM1B is used with a single phase power source. I got 2 complete RCM1A cabinets and a RCM1A panel out of the cabinet that were left over from the Sherman Texas siren removal of a couple of years ago. They had been sitting out in the weather since the removal without the lids on them. The picture on the left is the best of the 2 cabinets just after I got them. You can see the ice in the corner next to the switches. The picture on the right is the same cabinet after I finished the restoration. After some rewiring, cleaning and rusty parts scrubbing the thing works great!

Big RCM Cabinet Pictures and Schematics
See the RCM1A cabinet up close.

Click below to see the schematic.

   

See the RCM1B cabinet up close.

Click below to see the schematic.


Chopper hookup and manual switchesChopper Pitch Control and Test Switch Panel
Here is a close-up of the chopper hook-up terminal strip, chopper auto-transformer and test switch panel. The switch panel allows each motor of the siren to be tested individually. Moving the respective switch to the test position manually activates that motor. The pitch of the siren can be changed by hooking up the chopper to the various terminal strip terminals. One wire of the chopper motor is connected to the far left terminal. The pitch is lowest when the other wire to the chopper is hooked up to the terminal second from the left and the pitch is highest when the other chopper wire is hooked to the far right terminal. This set up varies the voltage to the chopper from 120 to 240 volts. As far as I know the Thunderbolt is the only siren that has an adjustable pitch like this. Click image to see larger.

Old RCM Cabinet Photo 1952
I found some old Thunderbolt siren photos on the Seattle Washington Municipal Archives web site. Included in their vast array of photos is this 1952 RCM cabinet photo. Since the Thunderbolt came out in 1952 this must be one of the first RCM cabinets sold. The Seattle Municipal Archives folks were kind enough to send me a high resolution scan of the negative of this photo. Just click on the photo to see the larger version.
The photos of the Seattle Thunderbolt siren are on the Siren Pictures page 2.
Federal Signal Siren Timers

The unit that actually controls the siren signal is called the timer. This timer is the early version of the Federal AR timer. The Federal timers use 3 minute timer motors which operate a system of switches to activate the siren signals. Federal still sells these timers for use with all their sirens not just the Thunderbolt siren. The type of timer pictured at right was sold by Federal up through some time in the 1960's, I believe. The box measures W12.5" x H9.5" x D6". The red lamp above the buttons activates when the timer is cycling. The top button on the front panel is the "Manual" button which operates the siren for only as long as the button is depressed. The second button from the top is the "Take Cover" signal which operates the siren in a on-off or wavering mode for 3 minutes. The bottom button is the "Alert" signal which operates the siren in a steady on mode for 3 minutes. To see a large version of this picture click the picture.

This is the inside of the old style version of the AR timer pictured above. You can see in this picture that the timer uses adjustable switch levers which are activated by a series of cams moved by the timer motor. I'm not sure if this timer's wiring is completely intact. The purple wires are connected to the power terminals of the terminal strip. This timer operates on 230 volts. To see a larger version of this picture click the picture.


This is the newer version of the Federal AR timer. Federal still sells this timer. This particular timer has "NOV 1986" stamped inside. The box measures W8.5" x H10.5" x D4".
The yellow lamp on the front of the box operates as long as the unit has power and the red lamp operates when the timer is cycling. This timer has the same functions as the above timer but the front panel is quite a bit different. The silver button on the front panel is the "Test" button which, like the "Manual" botton on the timer above, operates the siren for only as long as the button is depressed. The blue button is the "Alert" signal which operates the siren in a steady "On" mode for 3 minutes. The yellow button is the "Attack" signal which operates the siren in a on-off or wavering mode for 3 minutes.signal and the black button is the "Cancel" button which stops the timer's control of the siren signal while the timer continues to run to the end of it's cycle. To see a large version of this picture click the picture.

This is the inside of the newer style Federal AR timer. The same principal as the older AR timer but with newer components. This unit uses microswitches, 3 rotating motor-driven cams, modular plug-in relays and will operate on 115 as well as 230 volts. Click on the picture to see a large picture of the inside of the newer AR timer.

Federal Signal AF Timer
Federal also produced an AF timer to be used with sirens to operate a "Fire" signal in addition to the usual "Alert" and "Attack" Civil Defense signals. The "Fire" signal would be used as a fire call signal for volunteer firefighters. Some sirens are still used for volunteer fire call-in. The fire signal is similar to the attack signal in that the siren turns on and off resulting in the up and down signal but also produces a "Hi-Lo" signal while the siren is in the "on" portion of the on-off cycle. When the siren runs in the off portion of the signal the Hi-Lo stops and the siren coasts down regularly. The Federal Thunderbolt 1003 and the Federal 3T22 were both capable of producing the fire signal. Click the AF timer photo to see a larger photo.
See the 3T22 Fire Siren Page Here.

Inside the AF timer.
This timer is pretty much the same as the AR timer above but has an additional motor-driven cam and relay to operate the fire signal. The hook-up schematic is missing from this unit.
Click the photo to see a larger photo.