Mucho Gracias El Pimperino.. Thanks Pimp for the plug,
This is my third time writing this since a faulty mouse on my fiance's cpu make the screen go back sometimes loosing everything I typed.
The federal Signal Twinsonic lightbar is the brain child of Earl Gosswiller, 1912-2009
http://www.airraidsirens.com/forums/viewtopic.php?t=5420&start=0&postdays=0&postorder=asc&highlight=&sid=00056d608838577aa9bb22073dbf4f6c
His ideas were put into patent in 1967 for a fully enclosed rotating beacon light that stretched acrossed the roof of patrol cars. The twinsonic was debuted at the 1968 International Association Fire Chiefs in Louisville Ky. The lightbar was as instant success. The lightbar sold more units in 1969 then the model 11 Visibar's past 2 years combined.The lightbar was built completely by hand until 1979 when a production machine was introduced that bolted the rotator bases down and the speaker tray.
The model 12 series A1 (1968-1972) was a 54" full size lightbar with 2 tall triple reflection mirrors mounted next to the rotators. the speaker trays were metal and the motor was flat on top and bottom and featured heavy duty windings and thick brushes. The first additions had black anodized aluminum frames and completely round bulb holders.
The next brain storm from Earl was the model 12X which took the 2 tall triple reflection mirrors and cut them horizontally and rotated the top half 180 degrees to face the rear. Now you had just as many flashes to the front as you did the rear.
The next product line was the 12F lightbar which originally consisted of 4
par 36 (4414) bulbs mounted next to the rotators and these flashed in a wig wag pattern to the front an rear. By 1972 this was replaced by the new style 12F with lower front fascing cascade and top flasher housing with 2 polycarbonate filters from cut down dietz lenses.
Series A1 also saw the second series motor come about. This motor had similar properties as the heavy duty model but the castings were different. The second series had an X in the cast.
In 1973 Federal Signal entered into an agreement to build a special service bar to meet California's stringent laws of solid red bulb to the front and a flashing amber bulb to the rear. This was the CTS series of lightbars
By 1974 they came out with a "small" line of Twinsonic lightbars that measured 47 1/4 inches in length. These were available in all the common models.
In 1974 they also came out with their Economy line which removed the stainless steel strips from the bar and replaced the stainless speaker cover with an aluminum one.
In 1977 Federal Signal introduced the "medium" line of twinsonics which measured 47 1/2 inches. These lightbars were available in all the common twinsonic models.
The infamous green domes came to fruition via a change in most state laws that required security vehicles to have green and amber domes on the lights while in motion. These domes were produced from 1979-1981.
I know there is more in my head... But I am tired and need some sleep!