NBC suit
An NBC (nuclear, biological, chemical) suit, also called a chemsuit or chem suit or chemical suit is a type of military personal protective equipment. NBC suits are designed to provide protection against direct contact with and contamination by radioactive, biological or chemical substances, and provides protection from contamination with radioactive materials and some types of radiation, depending on the design. It is generally designed to be worn for extended periods to allow the wearer to fight (or generally function) while under threat of or under actual nuclear, biological, or chemical attack. The civilian equivalent is the Hazmat suit. The term NBC has been replaced by CBRN (chemical, biological, radiological, nuclear), with the addition of a new threat, radiological, meaning radiological weapon.
NBC chimes
The use of signalling tones to indicate the end of a program would be unique to the NBC networks. The CBS Radio network, founded in 1927, never adopted anything similar, instead keying its network switching to the standard phrase "This is the Columbia Broadcasting System". Initially NBC had two national networks, the NBC Red Network and the NBC Blue Network, however the Federal Communications Commission (FCC) was unhappy with this and worked to eliminate the common ownership. In late 1942 Phillips Carlin became vice president of programming at the soon-to-be independent Blue network, which later became the American Broadcasting Company (ABC). One of his first decisions was whether to adopt "a new set of chimes (as distinguished from the NBC chimes now in use)", and the choice was to instead end their use on the Blue network. However, the remaining NBC network operations considered the chimes to be an important part of their corporate identity. In 1942, NBC estimated that the average listener heard the tones 16 times a day, while annually there were nearly 20 billion impressions worldwide.