Echo One was the first subspace amplifier deployed by the United Earth starship Enterprise NX-01. It was deployed in August 2151. (ENT: "Fortunate Son")
In September 2151, Echo One was destroyed, along with Echo Two, by an unknown alien vessel. (ENT: "Silent Enemy")
Echo One was used by Vice Admiral Forrest to relay a Vulcan request for assistance at Paan Mokar to Enterprise in 2152, suggesting it had been replaced. (ENT: "Cease Fire")
According to Star Trek: Star Charts (p. 60) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), Echo One was located in the Beta Quadrant.