From the fall of Morris Island in early September 1863 until February 1865, the garrison at Fort Sumter remained vigilant. Though, by spring of 1864, several attempts had failed, the fort’s defenders stood watch looking for any moves by the Federals against the fort. It was one of the longest (if not the longest) continually manned picket during the Civil War.
In the case of an attack, the garrison had to move quickly and prepare to confront the threat. But to remain protected by the fort’s remaining structure, the garrison remained well below the parapets. To achieve the minimum reaction time, in February 1864 the Confederates implemented an interesting alarm system. Captain John Johnson detailed this in his post-war history of the siege, The Defense of Charleston Harbor:
This was the period marked by the introduction of something quite new in the defense of fortresses. A post so advanced as Fort Sumter had become since September was perilously isolated, and on the dark nights greatly exposed to capture from assault. Everything in such a case depended on the promptest manning of the walls to repel attack; and to effect this General Beauregard suggested that a system of bell-ringing be used throughout the fort to communicate the alarm from the lookout sentinel on the wall or in the breach to the commanders of detachments in the bombproof quarters of the garrison. The plan ordered was executed without delay, and from four points on the crest of the ruins the signal of danger could be transmitted by the sentinel or his officer touching a bell-pull. This at once rang the alarm in the soldiers’ quarters down below in the cavernous recesses of gallery and casemate, otherwise only to be reached with a delay that might have proved fatal. The system was maintained in perfect working order from this time in February to the end of the defense in the same month of the following year. It was a mode of alarm as startling as it was complete, and few of the surviving defenders of Fort Sumter in those long watches of the night will be apt to forget the use of those bells, with the turning-out of the garrison to meet a threatened assault.
Very simple application, using an item readily available. Sounds so simple that I would cast some doubt on Johnson’s claim about the “introduction.” On the other hand, not having details of the arrangements, perhaps this was more than a simple bell and a string.
(Citation from John Johnson, The Defense of Charleston Harbor: Including Fort Sumter and the Adjacent Islands, 1863-1865, Walker, Evans & Cogswell Company, 1890, pages 201-2.)