The Beardslee Telegraph was a portable military telegraph developed by George Beardslee and adopted by Albert Myer to provide a mobile field telegraph system. The instrument was operated by hand-turned magnetos and did not require the heavy batteries needed in the civilian telegraphs. It included an alphabet dial and pointer instead of the usual key for transmission.
Limitations of the instrument were its short range of about ten miles due to insufficient power, slow transmission, and frequent lack of synchronization between sending and receiving sets. It was first used 24 May 1862 in the Peninsular campaign. Its first major triumph was during the Battle of Fredricksburg when it provided Burnside with communications across the river when fog and smoke had rendered the usual visual signal communication impossible.
Its popularity declined after this battle because it was often competing with the faster and more powerful commercial telegraph facilities. In November 1863, most of the equipment was discarded. Only the insulated field wire remained in military use.