Lives often hung in the balance when messages were sent to to warn ships of the presence of Ice Bergs. Ships safety depended on the constant around the clock headphone monitoring maintained by the ships Radio Officers. All lives on board could depend on Just one Fragile Contact Point, that between the metal (cats whisker) and the delicate sensitive point on a piece of galena, clamped firmly in the contact cup of the detector mounted on the control panel of the receiver. 

Long before the invention of the first point contact transistor, the two cats whisker crystal was a forerunner to the solid state diode. The switchable plan B, for backup, was the pathfinder in the provision of redundancy, often needed in todays ruggedised communications equipment and the forerunner in the Invention of the transistor. 

Plan B backup in Ships Communication was needed when an unexpected lightening strike could require the Switch Over to the Reserve signal detector. This stressful event could happen in the middle of decoding the Morse message, and noting it

down in the signals record log book, where these Morse Code messages were required to be stored.