KG-84
The KG-84A and KG-84C are encryption devices developed by the U.S. National Security Agency (NSA) to ensure secure transmission of digital data. The KG-84C is a Dedicated Loop Encryption Device (DLED), and both devices are General-Purpose Telegraph Encryption Equipment (GPTEE). The KG-84A is primarily used for point-to-point encrypted communications via landline, microwave, and satellite systems. The KG-84C is an outgrowth of the U.S. Navy high frequency (HF) communications program and supports these needs. The KG-84A and KG-84C are devices that operate in simplex, half-duplex, or full-duplex modes. The KG-84C contains all of the KG-84  and KG-84A modes, plus a variable update counter, improved HF performance, synchronous out-of-sync detection, asynchronous cipher text, plain text, bypass, and European TELEX protocol. The KG-84 (A/C) is certified to handle data at all levels of security. The KG-84 (A/C) is a Controlled Cryptographic Item (CCI) and is unclassified when unkeyed. Keyed KG-84 equipment assumes the classification level equal to that of the keying material used. Characteristics. Operating temperature. Operating temperature: 0 to 55 °C MTBF. 69,000 hours (7.9 years)