This SR-209 is a surveillance receiver for surveillance and countermeasures job , developed around 1965 by Astro Communication Laboratory (ACL) in Gaithersburg (Maryland, USA). It covers a frequency range of 2 MHz to 12 GHz 1 spread over several frequency bands, each requiring a specific plug-in unit. 

The SR-209 was one of the standard receivers of the US Central Intelligence Agency (CIA).

The receiver is suitable for the reception of AM, FM and CW signals, and also for pulse-modulated signals, which were generated by some of the CIA's covert listening devices (bugs)of the era.