Murdock Spark Key
|This radio transmitting key
was made by the William J. Murdock Company of Chelsea, MA circa
1915. It is typical of keys of the day, having 1/4 inch silver
contacts as needed to handle the primary circuit current of a spark
transmitter. It could be purchased with larger contacts (up to 1/2
inch) for heavier duty applications. The remaining metal parts are
nickel-plated brass, and the marble base measures about 3 by 5 inches,
and is about 3/4 inch thick.
Where it differs from most other keys, however, is the double knob arrangement which brought the operator's hand down closer to the mounting surface. This was surely meant to reduce fatigue and carpal tunnel problems. I don't know whether this key was purchased this way, or the second knob was an aftermarket gadget. Unfortunately, it did nothing to isolate the operator from the potentially lethal voltages that were present on the metal parts of the key.