Insignia Description
A Silver color metal and enamel device 1 1/8 inches (2.86 cm) in height overall consisting of a shield blazoned: Argent, on a pile Tenné a bell of the first, two flaunches of the second, fretty of the field; attached below the shield a Silver scroll doubled Orange and inscribed "VIDEO ET MONEO" in Black letters.

Symbolism
In the orange and white of the Signal Corps, the wedge-shaped pile is symbolic of the driving force of the organization, the bell representing contact. The V-shaped pile is also symbolic of victory; the interlacing or grill on each side represents the plotting functions of the organization. The motto is translated "I WATCH AND WARN."

History
The distinctive unit insignia was originally approved for the 551st Signal Aircraft Warning Battalion on 20 December 1942. It was redesignated for the 551st Signal Battalion effective 16 September 1986.

Source: The US Army Institute of Heraldry