Connector Terminology Explained: An Illustrated Glossary

The connector field guide

An illustrated glossary of the parts, properties and processes behind electrical connections.

StructurePerformanceMaterialsSignals

A contact carries current.
A housing locates it.
A rating describes its limits.

Connector language mixes part names, manufacturing methods and measured properties. A “socket” might mean a contact or a complete connector; “voltage” might refer to normal operation or an insulation test. Start with the term you need, or follow the seven topics from physical structure to signal behavior.

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01

Parts & structure

Follow the path from the mating face to the cable. Contacts carry current; the surrounding parts locate, protect and support them.

Connector

A component that joins electrical paths between wires, cables, circuit boards or equipment. Many connectors make a separable connection; the word may refer to one half or to a mating pair. This glossary focuses on electrical connectors, including RF and high-speed types.

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Contact / terminal

A contact is the conductive part that engages its mate. A terminal is a conductive connection point or part used to terminate a wire or circuit. The names overlap in catalogs: a crimp contact can have a mating end and a wire-terminal end.

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Pin contact / socket contact

A pin contact enters a socket contact; the socket grips the pin with a conductive contact surface. These are often called male and female contacts. The shape of the outer shell alone does not tell you which contact is inside.

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A connector, from front to rearView full size

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Conceptual longitudinal cutaway: contacts pass through an insulating insert inside a shell; a coupling ring surrounds the front and a cable exits at the rear.
Conceptual section of a circular connector; parts and construction vary by family. Individual parts may be combined in a single molded body.

Housing / shell / insert

Housing is a broad name for the body that supports a connector’s parts. A shell is its outer protective structure. An insert holds contacts in their positions and electrically separates them. Depending on the design, these functions may be separate parts or combined in one molded body.

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Backshell

A rear accessory fitted to a connector shell. It can organize the cable exit, support a clamp, terminate a cable shield or accommodate seals. A backshell and a flexible strain-relief boot can appear together; they have different mechanical roles.

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Coupling nut

A rotating ring that secures the mating halves, commonly by a thread. It is different from a panel-mounting nut, which fixes one connector to a wall or panel. The contacts do not need to rotate with the coupling nut.

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Latch

A mechanical catch that holds a connection closed until released. A latch may be part of a plastic housing, a metal clip or a separate mechanism. Its retention function is distinct from the spring pressure between electrical contacts.

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Key / keyway

A key is a projecting alignment feature; a keyway is the matching recess or channel. Their locations guide insertion and can block the wrong orientation or an incompatible variant before the contacts engage.

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Seal / gasket / O-ring

Seal describes a barrier against leakage or ingress. A gasket seals between joined surfaces. An O-ring is a ring with a circular cross-section that seals when compressed in its intended groove. A connector may need separate seals at its mating face, panel and cable entry.

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Grommet

A flexible part surrounding a wire or cable at an opening. It can cushion the wire against an edge and, in a sealing design, close the gap around it. Unused wire cavities may require separate sealing plugs.

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Strain relief

A feature that transfers cable pulling or bending loads away from electrical terminations. Examples include a cable clamp and a flexible molded boot. Their shapes and load paths differ; a decorative sleeve is not automatically an effective strain relief.

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Mating interface

The geometry and arrangement where two connector halves meet: contacts, guiding surfaces, keys and any interface seals. Sharing an interface name does not by itself establish the wiring or performance of a complete cable assembly.

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02

Interfaces & terminations

Mounting describes where a connector is supported. Termination describes how its contacts join a wire or a circuit board.

Plug / receptacle / jack

Plug and receptacle describe the mating components according to a connector family’s naming convention. A receptacle is often fixed to equipment, while a plug is often on a cable; inline exceptions exist. Jack commonly names the receiving component in RF and other interfaces. Contact gender must be identified separately.

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Both are plugs. Their center contacts differ.View full size
SMA plugPin center contactMale contact
RP-SMA plugSocket center contactFemale contact
SMA and RP-SMA illustrate why “plug” is not a reliable substitute for “male contact.” TE Connectivity / Linx — RF connector catalog, pp. 44–45.

Pitch

The center-to-center distance between adjacent contact positions in a stated row or pattern, usually in millimeters. Multi-row connectors can have different row and column pitches. Pitch is not the free air gap between the metal surfaces.

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Pitch and edge spacingView full size

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Two circular contacts. Pitch spans their centerlines; the smaller edge-to-edge distance spans the facing metal surfaces. No dimensions are assigned.
Pitch measures contact positions. Air spacing measures the gap between conductive surfaces.

Positions / populated contacts

Positions count the available contact locations. Populated contacts count those actually installed. A six-position housing can therefore contain fewer than six contacts. Blank positions may serve keying, spacing or assembly needs; the drawing identifies the intended arrangement.

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Keying / polarization / coding

Polarization prevents an unintended mating orientation. Keying uses geometric features to guide or restrict mating. Coding distinguishes variants within a family, sometimes using different key locations. For example, M12 A-coding describes an interface variant; it does not name a universal wire-color scheme.

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Panel mount / PCB mount / cable mount

A panel-mount connector attaches to an enclosure wall. A PCB-mount connector attaches to a printed circuit board. A cable-mount connector terminates a cable. These descriptions can overlap: a panel receptacle may also have leads soldered to a PCB.

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Straight / right-angle

These describe the relation between the mating direction and the cable exit or board connection. A right-angle cable connector turns the cable path relative to the mating axis. For board connectors, the drawing clarifies orientation relative to the board.

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Crimp termination

A wire connection made by controlled deformation of a contact barrel around a conductor. It joins the materials mechanically and electrically without solder. Some contacts have a separate insulation support crimp; that support does not replace the conductor crimp.

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Solder termination

A termination made with a solder alloy that bonds the conductor to a contact or board pad. Solder cups accept wires; solder tails connect to PCB pads or holes. The contact’s mating surface is a different region from its soldered termination.

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Press-fit

A solderless PCB connection in which a contact is pressed into a specified plated hole. A compliant section can deform to maintain pressure against the hole wall. Press-fit describes the board termination, not the way the connector’s mating halves lock together.

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SMT / through-hole

Surface-mount technology (SMT) joins component terminations to pads on the board surface. Through-hole leads enter holes in the board, commonly for soldering. Press-fit also uses plated holes, but forms its connection through mechanical interference rather than a solder joint.

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From contact to circuit boardView full size
Before soldering

The same metal pin forms the mating end and the board tail. The insulating carrier holds the eight pins apart.

Inside one soldered terminationView full size

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A continuous pin passes through an insulating carrier into a plated PCB hole. Solder bonds the tail to the copper hole wall and surface pads; PCB laminate surrounds the joint.
Two different jobs: the carrier locates the contacts; the soldered connection joins each tail to the board’s conductive features. The underside view shows the tails and copper pads before soldering; the section shows a soldered joint.
Conceptual geometry, with layer thicknesses enlarged for clarity. Board traces and other layers are omitted. This is not a product drawing or a solder-joint acceptance guide. Header construction reference · Through-hole soldering reference.

Cable assembly / wire harness

A cable assembly combines cable with the required terminations and other parts; it may be single-ended. A wire harness groups and routes multiple wires or cables, often with branches and several endpoints. Usage overlaps, so the assembly drawing gives a clearer picture than the label alone.

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03

Electrical terms

Current flows through the intended conductive path. Insulation keeps that path separated from other circuits and accessible parts.

Rated current

The current a specified contact or connector can carry under stated conditions. Ambient temperature, wire size, the number of loaded contacts and allowable temperature rise all matter. A per-contact value obtained with one contact loaded may differ from the value when every contact carries current.

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Rated / working voltage

Working voltage describes the voltage present during normal operation. A rated voltage states a manufacturer’s assigned operating value under specified conditions. AC RMS, AC peak and DC are different descriptions; a bare voltage number leaves an important part of the rating unstated.

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Dielectric withstand voltage

A specified test voltage applied across insulation for a stated duration to check for breakdown or other defined failure. The test can use AC or DC. Passing it does not make that test voltage the connector’s continuous working voltage.

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Contact resistance

Resistance through a mated contact connection, often reported in milliohms (mΩ). The measured result depends on where the test probes are placed and on the test method. Small contact spots and surface films affect the interface; conductor resistance can also contribute over the measured length.

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Insulation resistance

Resistance between points that should be electrically isolated, such as adjacent contacts or a contact and shell. It is commonly measured with a specified DC voltage and reported in megohms (MΩ) or higher units. It measures leakage through or over insulation, rather than resistance along the intended current path.

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Voltage drop

The difference in voltage across a current-carrying part. For a resistive connection, ΔV = I × R. Increasing either current or resistance increases this drop. Resistance can change with temperature and contact condition, so a calculated example is not a substitute for an assembly rating.

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Leakage current

Current flowing through a path intended to provide insulation. Insulating material and contamination on its surface can contribute. The test voltage, humidity and measurement arrangement affect the result. Leakage current and useful load current describe different paths.

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Temperature rise

The increase in the measured part’s temperature above the defined ambient or reference temperature. It is a temperature difference, not the final absolute temperature. Resistive heating follows P = I²R for the resistance being considered; heat removal determines the resulting temperature rise.

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Creepage / clearance

Clearance is the shortest distance through air between conductive parts. Creepage is the shortest path along a solid insulating surface between them. A groove can lengthen the surface path without increasing the direct air gap. Required distances depend on the applicable insulation rules and operating conditions.

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Clearance crosses air; creepage follows insulationView full size

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Conductors on each side of a groove. The clearance path crosses directly through air. The creepage path follows the solid surface down, across and up the groove. Conceptual section without assigned dimensions.
A sufficiently defined groove can extend the surface path. This sketch explains the distinction; it is not a spacing or voltage design rule. Texas Instruments — creepage and clearance.

Continuity / open circuit / short circuit

Continuity means an electrical path exists between specified points. An open circuit interrupts an intended path. A short circuit creates an unintended low-resistance connection between points that should remain separate. A continuity beep alone does not establish current capacity, insulation quality or high-speed signal performance.

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04

Contact mechanics

A connector is an electrical component with moving, loaded surfaces. Several different forces act at the same time.

Normal contact force

The force pressing mating contact surfaces together, perpendicular to their local interface. A deflected spring contact often supplies this force. It influences the actual conducting contact spots, friction and wear; it is not the same quantity as the force used to push a whole connector together.

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Two forces, two directionsView full size

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A pin enters from the left. Socket spring beams press on the pin from above and below, perpendicular to its sliding direction. The diagram distinguishes contact normal forces from the axial insertion force.
The socket presses across the pin while the pin slides along the mating axis. Contact friction is one contributor to the total mating force.

Mating / unmating force

The force needed to engage or separate the mating parts, measured under a defined procedure. Contact friction, seals and guiding features can all contribute. Rotating a threaded coupling introduces a torque, usually expressed in N·m, which should not be confused with a linear force in newtons (N).

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Contact retention

The resistance of a contact to being pushed or pulled out of its intended position in the housing. It concerns the contact-to-housing attachment. Connector latch retention and wire pull-out strength describe other joints and require different tests.

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Mating cycles / durability

One complete mating and unmating sequence is a cycle. Durability describes how many specified cycles a connector can undergo while meeting the defined acceptance criteria. A cycle rating is not a direct prediction of service years, and it does not automatically permit connecting or disconnecting under load.

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Contact wipe

The sliding movement between contact surfaces as they engage. Wipe can help disrupt surface films and establish contact, but it also produces wear. The wiping distance is only the portion with surface contact, not necessarily the connector’s full insertion travel.

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Creep / stress relaxation

Creep is time-dependent deformation under a sustained load. Stress relaxation is a reduction in stress while deformation is held fixed. In a mated spring contact, relaxation can reduce the force pressing against its mate over time, especially at elevated temperature.

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Fretting corrosion

Small repeated movements at a contact interface can wear the surface and produce debris. Where oxidation of exposed material or wear debris accompanies this movement, the process is called fretting corrosion. It can raise resistance even though the connector has never been deliberately unplugged.

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Tolerance

The permitted variation of a dimension or other specified characteristic. Parts must work together across these allowed variations. A nominal diameter alone does not describe the mating fit: the size limits, alignment and geometry also influence how the parts assemble.

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05

Environment & protection

A protection label describes a particular exposure or test. Dust, moisture, impact and combustion are different questions.

IP rating

An enclosure protection code defined by IEC 60529. The first characteristic numeral concerns access to hazardous parts and solid foreign objects; the second concerns water ingress. For connectors, the stated protection may require the halves to be fully mated or a specified cap to be fitted.

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Sealed / hermetic

An environmentally sealed connector limits ingress under specified conditions. Hermetic describes a gas-tight barrier evaluated against a defined leak-rate requirement, often achieved with glass-to-metal or ceramic seals. An IP water-protection rating alone does not establish hermetic performance.

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Operating temperature

The temperature range within which a component is specified to operate under its stated conditions. Current-generated heating and the temperature limits of contacts, housing, seals and cable can constrain the assembly. A brief soldering temperature or a resin’s heat-deflection temperature is a different property.

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Vibration / mechanical shock

Vibration is repeated mechanical motion; shock is a transient mechanical event. Tests describe the applied motion or pulse, its severity, duration and directions. Connector acceptance may include physical condition and electrical interruptions. A passing vibration result does not imply that every shock exposure is covered.

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Temperature cycling

Repeated movement between specified temperatures, with defined dwell and transition conditions. Different materials expand and contract by different amounts, loading joints and seals. A cycle test probes the effects of changing temperature; a steady high-temperature exposure probes a different condition.

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Damp heat

Exposure to elevated humidity and temperature to evaluate moisture-related changes. Steady-state and cyclic methods differ, including whether condensation occurs. Moisture can affect insulation, corrosion and materials even when no water jet or immersion test is involved.

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Salt spray

A controlled exposure to a salt-containing mist used to evaluate corrosion behavior. Hours in the chamber are a test duration, not a direct conversion to years outdoors. Specimen preparation, coating condition and acceptance criteria are needed to interpret the result.

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UL 94 flammability

A classification of how plastic specimens behave under specified small-scale flame tests. Ratings such as HB and V-0 use different test arrangements and criteria. The classification belongs to a particular material formulation and tested thickness; V-0 does not mean noncombustible or fireproof.

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06

Materials & manufacturing

The spring underneath, the surface finish and the insulating body do different jobs. Their names should not be treated as a single quality ranking.

Base material / plating

The base material supplies the bulk of a part’s structure. Plating is a deposited metallic surface layer. For a contact, the base alloy contributes conductivity and mechanical behavior, while plating changes the properties of the mating or termination surface. One contact can have different finishes in different regions.

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A plated contact is a layered materialView full size

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A conceptual cross-section shows a thin gold mating finish above a nickel underplate and copper-alloy base. Layer thicknesses are exaggerated and are not specifications for a product.
The spring substrate and surface finish serve different functions. Other finishes and layer arrangements are also used. Samtec — underplating and base metals.

Brass / phosphor bronze / beryllium copper

These are families of copper alloys. Brass is principally copper-zinc; phosphor bronze is a copper-tin alloy with phosphorus; beryllium copper contains beryllium and is available in heat-treatable grades. Strength, conductivity and spring behavior depend on the exact composition, temper and processing. The family name alone does not give those values.

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Gold / tin / silver plating

These finishes offer different contact-surface behavior. Gold resists oxidation and is widely used for signal contacts. Tin is economical but its surface oxide and fretting behavior require suitable contact design. Silver offers high conductivity and is used in many power contacts, while tarnishing behavior matters in its intended environment.

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Nickel underplate

A nickel layer between the base metal and an outer finish, often gold. It can act as a diffusion barrier and support the plated surface. Its purpose differs from that of the exposed mating finish; a gold-looking contact may therefore contain more than two material layers.

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Plating thickness

The thickness of a deposited layer, commonly stated in micrometers (µm) or microinches (µin). Location matters: a contact may be selectively plated only at the mating zone. More thickness is not a complete quality specification; layer composition, porosity, hardness and the underlying finish also matter.

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PA66 / PBT / LCP / PPS / PEEK

These identify polymer families used in engineered parts. Fillers, reinforcement and additives create grades with different properties within each family. A connector body’s material name does not by itself establish its operating temperature, flame classification or chemical resistance.

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Five polymer abbreviations decoded
AbbreviationNameWhat the abbreviation identifies
PA66Polyamide 66 (nylon 66)A particular polyamide family
PBTPolybutylene terephthalateA thermoplastic polyester
LCPLiquid crystal polymerA family with ordered molecular structures
PPSPolyphenylene sulfideA high-performance thermoplastic family
PEEKPolyetheretherketoneA member of the polyaryletherketone family

The grade supplies the missing detail: reinforcement, additives and test conditions. Heat-deflection temperature measures deformation under a specified load; it is not a continuous-use temperature rating.

Thermoplastic / thermoset

A thermoplastic softens with heating and can be processed again within its usable thermal limits. A thermoset forms a cross-linked structure during cure and cannot simply be remelted and reshaped. These describe material behavior, not a universal ranking of connector durability.

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Stamping / machining

Stamping cuts and forms metal sheet or strip using tooling. Machining removes material from stock to create the part. Both processes can produce electrical contacts; geometry, alloy, finish and contact design determine the result, rather than the manufacturing label alone.

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Injection molding / overmolding

Injection molding forms a part by injecting moldable material into a cavity. Overmolding forms material around an existing part or assembly, such as a cable termination. A molded cable exit can provide support and protection, but a specific ingress rating depends on the complete sealing design.

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07

RF & high-speed signals

At higher frequencies, a connection affects the shape and propagation of a signal as well as carrying current.

Characteristic impedance

The voltage-to-current ratio of a traveling wave on a transmission line. It depends on the line’s geometry and materials and is expressed in ohms (Ω). A nominal 50 Ω coaxial interface is not a 50 Ω DC resistor inserted in series with the signal.

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Insertion loss

The reduction in transmitted signal caused by inserting a component or channel, stated for defined frequencies and reference conditions. As a positive loss in dB, a smaller value means less loss. A network analyzer may instead show transmission magnitude, such as S21, as a negative dB value.

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Return loss

A measure of how little signal is reflected back from an impedance mismatch. Using the usual positive return-loss convention, a higher dB value means less reflection. The same reflection may appear as a negative S11 magnitude on an analyzer; the sign convention changes how the number is written.

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VSWR

Voltage standing wave ratio: the maximum to minimum voltage magnitude of the standing-wave pattern along a transmission line. It expresses mismatch without a dB unit. The ideal matched value is 1:1; larger ratios indicate more reflection. VSWR does not separately measure dissipative transmission loss.

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Follow the signal in both directionsView full size

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An incident signal reaches an interface or channel. Transmission continues forward; reflection returns toward the source. Arrow widths are illustrative, not measured amplitudes.
Arrow size is illustrative. Reflected energy and energy dissipated in a channel are different contributions to reduced transmission.
The same reflection, expressed three ways
Return lossReflected powerVSWR
10 dB10%1.92:1
20 dB1%1.22:1
30 dB0.1%1.07:1

Calculated for the usual real reference impedance: |Γ| = 10−RL/20, reflected-power fraction = |Γ|², and VSWR = (1 + |Γ|)/(1 − |Γ|). Values are rounded. These conversions describe mismatch, not the insertion loss of a complete cable.

Crosstalk

Unwanted signal coupling from one circuit or signal path into another. Near-end crosstalk (NEXT) is observed at the same end as the disturbing source; far-end crosstalk (FEXT) is observed at the opposite end. Contact arrangement, spacing, shielding and the complete channel influence it.

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Shielding effectiveness

How much a shield reduces electromagnetic coupling under a defined test, commonly expressed in dB versus frequency. A connector shell, cable shield and their terminations form part of the shielding path. A metal enclosure or braided cable alone does not establish the effectiveness of the complete assembly.

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Differential pair

Two conductors that carry a signal represented by the voltage difference between them. The receiver responds to that difference. Noise coupled equally into both can be rejected within the receiver’s limits; imbalance and unequal propagation can reduce that benefit. A pair still needs an appropriate electromagnetic return-path environment.

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Bandwidth / data rate

Bandwidth describes a usable frequency range or frequency span, measured in hertz. Data rate describes how many bits are carried per second. They are related through modulation, coding and channel behavior, but GHz and Gb/s are not interchangeable units. A connector’s frequency specification alone does not define a complete link’s data rate.

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Further reading

Technical references

Manufacturer explanations, material data and standards organizations provide more detail on these concepts.

  1. Amphenol Socapex — connector glossary
  2. Amphenol Aerospace — connector terminology
  3. Davide Andrea — The Electronic Connector Book, glossary
  4. TE Connectivity / Linx — RF connector catalog, pp. 44–45
  5. Amphenol — connector termination styles
  6. TE Connectivity — truck, bus and off-road solutions glossary
  7. Samtec — current-carrying capacity and loading conditions
  8. Harwin — Datamate T-Contact technical presentation
  9. Samtec — qualification report: insulation resistance and voltage withstand
  10. Texas Instruments — creepage and clearance
  11. Materion — stress relaxation of contact materials
  12. Samtec — contact design and plating
  13. Samtec — underplating and base metals
  14. IEC — IEC 60529, degrees of protection provided by enclosures
  15. Phoenix Contact — protection ratings and mated conditions, 1329943
  16. IEC — IEC 60068-2-14, change of temperature
  17. ASTM — B117, salt spray apparatus; significance and use
  18. UL Solutions — combustion tests for plastics
  19. Copper Development Association — C17200 alloy data by temper
  20. Celanese — engineered materials and polymer families
  21. Victrex — PEEK 450GL30 BLK technical data
  22. Ensinger — thermoplastic composites and processing
  23. Keysight — reflection measurements
  24. Rohde & Schwarz — antenna basics, VSWR
  25. Texas Instruments — the transmission channel
  26. TE Connectivity — EMI connector gaskets
  27. Renhotec — M12 4-pin female overmolded cable assembly
  28. IEC — IEC 60068-2-30, damp heat, cyclic
  29. IEC — IEC 60068-2-78, damp heat, steady state
  30. Copper Development Association — phosphor bronze for connectors
  31. Copper Development Association — brass alloy compositions
  32. Samtec — connector plating FAQs
  33. ZwickRoell — testing of plastics and rubber, creep tests
  34. IEC — IEC 60512-13-2, insertion and withdrawal forces
  35. TE Connectivity — quality handbook, silver tarnish
  36. Texas Instruments — data transmission terminology
  37. Phoenix Contact — IP code and multiple protection ratings

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