What did the declassified documents reveal?

COLD OPEN This is a declassified Central Intelligence Agency record titled Introduction to the SIGINT Installation Series, China, dated October 1967. The document provides an early overview of Chinese Communist signal‑intelligence facilities and was made publicly available through The Black Vault archive. PROVENANCE The record was released to the public via The Black Vault on the archive page for the CIA collection, with the declassification authority cited as the Central Intelligence Agency. The full text is accessible at the archive dot org link for the CIA record. THE DOCUMENT Introduction to the SIGINT Installation Series, China. Declassification review by N I M A slash D O D. October 1967. Copy one hundred sixteen, four pages. Approved for release. This report introduces an N P I C series of reports on the Chinese Communist S I G I N T facilities and is a partial answer to N S A requirement N S A slash S O C slash R nine six dash six seven. The series will consist of short individual reports which will use a standard format. This series of reports will include all suspect and known thick eight and fix eight facilities as well as those identified for future Chinese S I G I N T facilities. The basic Chinese S I G I N T facility consists of a thick eight or fix eight as a radio direction finder. These facilities, which are capable of determining both signal azimuth and frequency, have some type of communications antenna associated with them. Although an effort has been made to identify these facilities in all frequency ranges, only thick eight and fix eight facilities in the M I and H I I ranges have been identified to date in China. The communications antennas associated with the S I G I N T facilities consist of or are a combination of fishbone, vee, horizontal dipole, or rhombic antennas. There is no apparent feature or characteristic which distinguishes these facilities from other communications facilities. Therefore, any communications facility within the proximity of the direction‑finding array is suspect and its description will be included in these reports. The World Aeronautical Chart number, Basic Encyclopedia number, N P I C number, and category code in the individual reports are unique identifying numbers and letters assigned to the thick eight components of the S I G I N T facilities. Similar identifying numbers and letters assigned to other components of the facility will be included in their descriptions. Thick eight array. The thick eight array (Figure one) is a small version of the N R U G array. The thick eight arrays identified to date in China appear to be similar to the thick eight array previously observed at location six. The functional uses of the array are audio direction finding, aid to air navigation, S I G I N T monitoring receiver, and communications receiving including both foreign and domestic intercept. The array may also serve a secondary function in air traffic control and nuclear event detection. Although the…

Why was this case declassified?

This material entered the public record through the U.S. declassification and Freedom of Information Act (FOIA) process. The originating source document is linked on this page so the citation chain is auditable.

CIA Introduction To The Sigint Installation Series

◆ BLUF — The short version

COLD OPEN This is a declassified Central Intelligence Agency record titled Introduction to the SIGINT Installation Series, China, dated October 1967. The document provides an early overview of Chinese Communist signal‑intelligence facilities and was made publicly available through The Black Vault archive.

Date: AUG 13 · 2026
Release: Declassified · U.S. public record (FOIA)
Source document: View the primary source document

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What was CIA Introduction To The Sigint Installation Series about?: COLD OPEN This is a declassified Central Intelligence Agency record titled Introduction to the SIGINT Installation Series, China, dated October 1967. The document provides an early overview of Chinese Communist signal‑intelligence facilities and was made publicly available through The Black Vault archive.
Why was this case declassified?: This material entered the public record through the U.S. declassification and Freedom of Information Act (FOIA) process. Storyflo narrates it directly from the public release.

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