Links to the Apparatus Manufacturer Logos and the Delivery Lists have been added back to the forums.
Actually Primary/Secondary systems were used in most big cities. Gamewell classified them as Type A manual systems. They required a central office with 24 hr operators who received and retransmitted alarms manually using transmitters. The systems you and I are used to seeing are the Type B or automatic systems that use a repeater. You have to remember before radio the telegraph system was used for communication between the C.O. and the fire houses. It was used for the same things we do with a phone. i.e. we need coal for the steamer or station furnace, we need hay for the horses, send maintainance and etc. A second factor in the Primary/Secondary system is battery power. In a larger city you have a great number of stations. The battery power required to maintain 100mils would be great if you consider all the recording and sounding devise coils that would in the circuit. At 2 volts per battery x2 you could imagine what the size of the battery room would have to be. The secondary circuit allowed a local battery in each station to power the station alarm equipment. Redundancy was another reason. Two ways to get alarms to the firehouses. As you can see form the illustration below the boxes are on circuits alone and the stations are on "alarm circuits" The description in the earlier Gamewell catalogs of a Type A system is this "The arrangemnet is such that alarms may be received from any or all circuits simultaniously, announced and recorded, without possibility of confusion or interference. Generally alrms are transmitted manually, by operators, to the fire stations over primary alarm circuits and confirmed over secondary circuits." I'm still researching this myself as every cities system had some unique characteristics. I will be going to Cleveland soon to deliver one of their watchdesks and will have full access to records and schematics of their system. I hopr to learn more then.
