Lubliner is correct
From age four to ten, I spent many shifts in the Hardman Tower with my father who was a telegrapher for the B&O; my father was a military telegrapher with the Army Air Corps during WWII . My Grandfather's career was also at Harman Tower; my grandfather was a military telegrapher with the Army Air Corps during WWI. My Great-Great Grandfather was the first family operator. Private William H. Helm was the Grandson of Major William Helm, my Revolutionary War Patriot.
Private William H. Helm, Infantry Attached to Regiment organized for railroad guard duty and served on line of the Baltimore & Ohio Railroad by detachments, January, 1863.
Private Helm was captured near Cumberland, MD., August 1, 1864; imprisoned Salisbury, Rowan, North Carolina and died Jan 12, 1865 (starvation.) In February 1865, Union prisoners at Salisbury were freed.