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Glossary of Connector Terms


Accessories Sometimes referred to as “Rear Accessories” or “Backshells” are mechanical devices such as strain reliefs, cable clamps, adapters, potting boots, etc., which are threaded onto the rear connector accessory threads of plug or receptacle connectors to make up the total connector assembly.

Adapter A threaded ring device screwed onto the threads of an 83723 Series III threaded receptacle to accept a quick disconnect plug.


Back Mounted Rear mounted – a connector with its mounting flange mounted inside of a panel or box.

Bayonet Coupling A quick coupling mechanism for mating a plug onto a receptacle utilizing three equally spaced pins protruding from the receptacle shell which engage corresponding ramps milled into the coupling nut of the mating plug. Mating and unmating is accomplished by rotating the coupling nut.

BIN Code Basic identification number - color bands on the wire barrel end of a contact to identify contact part number. Each BIN number corresponds to one and only one slash sheet (XX) thus identifying the complete M39029/XX-BIN part number.

Boot A form placed onto the boot adapter used to environmentally seal and/or strain-relieve a cable assembly.

Boot Adapter A mechanical device with one side threaded onto the accessory thread of a connector (plug or receptacle) and the other side used to accept a boot.

Braid Braided wire – flexible conductor made of woven or braided assembly of wires.

Bussing The joining of two or more circuits.


Cable Clamp A mechanical device attached to the accessory threads at the rear of a plug or receptacle to support the cable or wire bundle, to provide strain relief and absorb vibration and shock which would otherwise be transmitted by the cable to the contact or wire crimp area.

Coaxial Contact A contact with two conductive surfaces – a center contact and a surrounding coaxial sleeve.

Color Coding A system of identification of contact insertion/extraction tools. Colors green, red, orange, blue, yellow and white indicate the proper tool to use for either insertion or extraction of appropriate contact size.

Connector A mechanical device, either a plug or a receptacle, used to terminate or connect electrical conductors (pin and socket contacts) of a cable and its individual wires and provide a means to continue or terminate these conductors to a mating connector which may be mounted on electrical equipment panels, thru bulkheads, printed circuit boards, etc.

Contact Pin or socket – the conductive element of a connector which actually makes contact for the purpose of conducting electrical current. This is the heart of the connector.

Contact Area The actual area in contact (touching) between two conductors (pin and socket) permitting the flow of electrical current.

Contact Arrangement The number of contacts, their size and spacing in a connector.

Contact Engagement/Separation Force The force necessary to engage or separate pin and socket contacts.

Contact Resistance The electrical resistance on a mated pair of contacts (pin and socket). Resistance is measured in ohms or millivolt drop at a specified current over the engaged contacts.

Contact Retainer Contact retention clip – a device captivated in the hard plastic of the connector body (insert) which retains the contact in the insert.

Contact Retention The axial load in either direction (push or pull) which a contact can withstand without being dislodged from its normal position within the insert of the connector.

Contact Size A specific number indicating the size (or gauge) of the engaging end of the contact; examples: size 20, size 16, size 8, etc.

Contact Shoulder The flanged portion around the body of a contact which limits its forward travel into the insert and prevents it from being pushed forward out of the insert.

Coupling Nut/Ring The movable portion of a connector plug which aids in the coupling and uncoupling of a plug and a receptacle and locks the plug and receptacle together.

Crimp The physical compression (uniformed deformation) of a contact wire barrel around the conductor in order to captivate the conductor and make an electrical connection.

Crimping A pressure method using a tool to mechanically secure a contact (pin or socket) to a conductor (wire).

Crimp Contact A contact, pin or socket, whose back portion (wire barrel) is a hollow cylinder into which a stripped wire (conductor) is inserted. The sidewalls of the wire barrel are then mechanically compressed (uniformly deformed) using a crimping tool to captivate the conductor.

Crimp Die Portion of the crimp tool that shapes the crimp on the wire barrel.

Crimp Tool Mechanical device that holds the crimp die and is used to perform the crimping function.


Depth of Crimp The distance the crimp die indenter penetrates into the wire barrel.

Die Closure The distance between the crimp die indenters when the crimp tool handle is at full closure. This is usually checked using a Go/No Go gauge.

Dielectric A material having electrical insulating properties.


Environmental Sealing Designed in a connector using grommets, interfacial seals, peripheral seals, gaskets or potting material to keep contaminants such as dirt and moisture out of the connector.

Extraction Tool Removal tool – a tool used to remove contacts from a connector.


Filter Contact A contact which provides filtering of EMI signals without altering its normal function.

Filter Connector A connector using filtered contacts or filtered discs to filter EMI signals without altering its normal function.

Front Mounting A connector mounted with its mounting flange outside of a box or panel.

Front Release A term indicating the direction the contact removal tool must enter the connector to allow for the removal of contacts. On a front release connector, the contact removal tool must be inserted in the contact cavity from the front or face of the connector to release the contact retention clip.Whether front release or rear release, the contacts are inserted from the rear of the connector.


Grommet A resilient elastomeric seal bonded to the rear of a connector. It is designed with internal sealing barriers that grasp and seal on the wire's insulation to prevent contaminants from entering into the rear of the connector.

Grounding Fingers Grounding spring – a metal band with spring fingers attached to the plug shell to ensure positive shell-to-shell grounding before the contacts engage during mating and when they disengage during unmating. They are also used to improve EMI/RFI performance.


High Density Connector A connector having its pins arranged close together without compromising system performance.


Insert The insulating core of the connector designed to position, retain, support and provide separation for the contacts.

Insertion Tool A tool used to insert contacts into a connector.

Inspection Hole A hole at the bottom of the contact wire barrel to permit visual inspection to ensure that the wire has been inserted to the proper depth in the wire barrel prior to crimping.

Insulation Jacket – insulating material around a wire or cable.

Interface The two surfaces on the contact side of a mating plug and receptacle. The surfaces will face each other and interface when mated.

Interfacial Seal The sealing of mating connectors over the entire area of the interface and around each contact. This is accomplished when resilient material, with raised barriers around each cavity on the pin interface, displaces into the hard recessed (chamfered) cavities on the socket interface. This creates what is commonly called “cork and bottle seal.”


Jacket Insulation – insulating material around a wire or cable.


Key A rectangular projection on plug connector shell designed to slide into the rectangular slot or keyway in the mating receptacle connector to properly align and guide the two mating halves together. Generally used to obtain proper polarization.


Lanyard A sturdy wire attached to plugs of certain connectors which allows unmating and separation of plug and receptacle by a pull on the wire (lanyard).

Locator Positioner or Turret head – a mechanical device attached to a crimp tool with multiple locators to position different size contacts for crimping. It is indexed to a proper position by rotating.


Mate The joining of two connectors.

Mated Pair A plug and receptacle joined or to be joined together.

Millivolt Drop Voltage loss due to resistance created by a crimp joint.


“O” Ring Also referred to as peripheral seal is used around the periphery of a connector shell and is compressed internally between the plug and receptacle shells when mated to prevent contaminants from entering the connector.


Pin Contact A “male” contact with the engagement end that enters into the socket contact.

Plating The overlaying of a thin coating of metal on connector shells and contacts to prevent corrosion, improve conductivity or provide for easy soldering. plug The “free to move” or “unmounted” member of a mated pair of connectors which contains the coupling ring/nut for coupling and locking the connectors together.

Polarization Also known as clocking or keying – the mechanical arrangement of inserts or rectangular keys (projections) and keyways (slots) to ensure proper mating. It eliminates errors when mating identical connectors mounted beside each other.

Positioner Locator or Turret head – a device attached to a crimp tool with multiple locators to position different size contacts for crimping. It is indexed to a proper position by rotating.

Potting The permanent sealing of the back of a connector, after the wires have been inserted, with a material to keep out the contaminants and/or provide strain relief.

Potting Boot A form fitted onto the potting ring , which is threaded onto the back of connector, to environmentally seal/strain relive a cable assembly.

Pull out Force The force necessary to separate a wire from the contact crimped to it or the force necessary to pull a properly seated contact from a connector by pulling.

Pull Test Tensile test – a controlled pull test on the contact crimp joint to determine its mechanical strength.


Range Wire range – the acceptable sizes of wires accommodated by a particular contact wire barrel size. Also the acceptable diameter of wires accommodated by a sealing grommet.

Rear Accessories Referred to as backshells, they are mechanical devices that screw onto the accessory threads on the rear of the connector. Includes strain reliefs, clamps, adapters, potting boots, etc.

Rear Mounted Back mounted – a connector with its mounting flange mounted inside of a panel or box.

Rear Release A term indicating the direction the contact removal tool must enter the connector to allow removal of the contacts. On a rear release connector the contact removal tool must be inserted into the contact cavity from the back or rear of the connector to release the contact retention clip.Whether rear release or front release, contacts are inserted through the rear of

the connector.

Receptacle The fixed or mounted member of a mated pair of connectors designed to be mounted to a box, panel or bulkhead.

Removal Tool A device used to remove contacts from a connector.


Safety Wire A means of putting wire through holes drilled in the coupling ring/nut of a connector plug, and securing the wire to a panel of bulkhead to prevent the plug from loosening or decoupling from the receptacle during vibration.

Scoop Proof A term to describe a longer shell design on the pin half (plug or receptacle) of a connector. The longer shell allows the pin contacts, which protrude from the face of the connector, to be recessed sufficiently so as not to be damaged if the mating shell is “scooped” into it during mating process. This prevents pins from being bent and/or contacts from being electrically shorted during mating. This is especially important when using size 22 contacts, which because of their small size, bend easily.

Sealing Plug A small plastic plug (MS27488-**-1, head first) inserted into the rear grommet of a connector, especially an environmental connector, to seal and prevent the entry of contaminants into any unused (unwired) cavities.

Selective Plating The applying of plating material to a limited area of a contact, especially areas susceptible to wear.

Service Rating The maximum amount of voltage or current a connector is designed to continuously carry.

Shell The outside case of a connector which holds the dielectric insert and contacts.

Shielded Contact A contact shielded from unwanted signals (EMI/RFI) by one or more outer (protective) conductors. These contacts are not generally matched to the impedance of the cable they terminate.

Socket Contact A contact whose engaging end is designed to accept the entry of a pin contact.

Solder Contact A pin or socket contact that accepts a conductor (wire) which is soldered onto the “solder cup,” not crimped into the wire barrel.

Splice Wire splice – a device used to join two or more conductors (wires). strip To remove insulation from a conductor. Generally for inserting the conductor into the wire barrel/solder cup of a contact for a crimping/soldering operation.


Tensile Test Pull test – a controlled pull test on the contact crimp joint to determine its mechanical strength.

Thermocouple Contact A contact made of special material, used in connectors in high temperature applications as a means of measuring temperature electrically.Materials often used for these contacts are alumel, chromel, constantan, iron and copper.

Threaded Coupling A means of coupling a mating pair of connectors by engaging threads on the exterior of a receptacle with interior threads of the plug.

Turret Head Locator or Positioner - a device attached to a crimp tool with multiple locators to position different size contacts for crimping. It is indexed to a proper position by rotating.


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