The GR connector, officially the General Radio Type 874, was a type of RF connector

RF connector

A coaxial RF connector is an electrical connector designed to work at radio frequencies in the multi-megahertz range.RF connectors are typically used with coaxial cables and are designed to maintain the shielding that the coaxial design offers. Better models also minimize the change in transmission...

 used for terminating coaxial cable

Coaxial cable

Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...

. Designed by the General Radio

General Radio

General Radio Company was a broad-line manufacturer of electronic test equipment. Started in Cambridge, Massachusetts in 1915, the company moved to West Concord in the 1950s. There, it became a major player in the automatic test equipment business, manufacturing a line of testers for assembled...

 Corporation, it was widely used on their electronic test equipment

Electronic test equipment

Electronic test equipment is used to create signals and capture responses from electronic Devices Under Test . In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired...

 throughout the 60s and 70s.

The connector had several desirable properties:

• Good control of the electrical impedance
  Electrical impedance
  Electrical impedance, or simply impedance, is the measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current circuit...
  
   across a wide range of frequencies
• Reliable mating
• Hermaphrodism
  Hermaphrodite
  In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
  
  , so there were no "male" or "female" connectors; any GR connector could mate with any other GR connector.

This last characteristic was achieved by having both the inner and outer conductors made from four leaves, two of which were displaced slightly outwards and two of which were displaced slightly inwards. By rotating one connector by 90 degrees, its inner leaves would mate with the other connector's outer leaves and vice-versa.

Adapters to other connector series were available.

Eventually, the high cost of the connector led to it being obsoleted by the much more common BNC connector

BNC connector

The BNC connector ' is a common type of RF connector used for coaxial cable. It is used with radio, television, and other radio-frequency electronic equipment, test instruments, video signals, and was once a popular computer network connector. BNC connectors are made to match the characteristic...

 and, for high-frequency applications, N connector

N connector

The N connector is a threaded RF connector used to join coaxial cables. It was one of the first connectors capable of carrying microwave-frequency signals, and was invented in the 1940s by Paul Neill of Bell Labs, after whom the connector is named.-Design:Originally, the connector was designed to...

s and SMA connector

SMA connector

SMA connectors are coaxial RF connectors developed in the 1960s as a minimal connector interface for coaxial cable with a screw type coupling mechanism. The connector has a 50 Ω impedance. It offers excellent electrical performance from DC to 18 GHz.-Connector design:The SMA connector consists of...

s. General Radio designed the incompatible Type 900 successor to the 874, to address the higher performance needs of the industry, but it was not very successful.