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The Crutchfield writing team is a group of full-time, in-house copywriters who share a passion for consumer electronics. In addition to creating the articles and videos you find in the Research area of the Crutchfield website, these hard-working and talented people write the informational copy for the products on our website and in the Crutchfield catalog. Our writers constantly research the latest products, technologies, and industry trends, so that we can bring you the most helpful information possible.

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5-way binding post speaker terminals 5.1-channel, 6.1-channel, and 7.1-channel inputs
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5.1-channel, 6.1-channel, and 7.1-channel inputs

These preamp-level analog inputs can be found on the back panels of some home theater receivers. A 5.1 input features jacks for 6 channels: left front, right front, center channel, left surround, right surround, and subwoofer (sometimes called "LFE" or "Low-Frequency Effects"). Because the LFE channel carries a limited range of frequencies, it's the ".1" in 5.1. A 6.1 input features the same jacks as a 5.1 input, but adds a back surround jack; a 7.1 input adds two back surround jacks.

Any of these multichannel inputs allow you to hook up a separate 5.1-channel surround sound (Dolby® Digital, DTS®) decoder, such as those built into some DVD and Blu-ray players. The extra jack(s) in 6.1 and 7.1 inputs have no current functionality unless you happen to be using a separate surround preamplifier with 6.1 or 7.1 processing — the main function of these extra jacks on a home theater receiver is to keep you ready for future gear and future surround formats.

5-way binding post speaker terminals

5-way binding posts are a versatile type of terminal used for amplified, speaker-level signals, usually found on higher-quality speakers and receivers. This kind of terminal accepts 5 kinds of speaker wire connections: bare speaker wire, pin connectors, spade connectors, banana plugs, and dual banana plugs. Some binding post connectors aren't considered "5-way," because they don't accommodate every one of these connection types.

5-way binding post speaker terminals 5-way binding post speaker terminals
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Each speaker (or each output channel on a receiver) uses a pair of binding posts for a single connection: one for the positive speaker lead (usually red), and one for the negative lead (usually black).




75-ohm coaxial jack

Sometimes called an "RF input," this kind of jack is commonly used for hooking up antennas, cable boxes, VCRs, TVs, etc. A 75-ohm coaxial cable can carry video and stereo audio information simultaneously. RF cable connectors (often called "F-type" connectors) either screw onto the 75-ohm jack, or just push on to connect.

75-ohm coaxial jack 75-ohm coaxial jack
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75-ohm coaxial connector 75-ohm coaxial connectors
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There are different types of coaxial cables. Standard coaxial cables are stamped "RG-59"; higher-quality "RG-6" cables feature better shielding, and exhibit less high-frequency loss over longer runs. (For connecting DBS satellite systems, it's essential to use an RG-6 cable to correctly pass the entirety of the digital signal.)

Coaxial digital jack

This type of jack is used for the digital audio inputs and/or outputs on A/V components such as receivers, CD players, DVD players, and more. Coaxial digital jacks are also sometimes found on higher-end PC soundcards for digital audio input and output.

Coaxial digital jack Coaxial digital jack
Coaxial digital connector Coaxial digital connector
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Coaxial digital inputs and outputs use standard RCA-type jacks (so coaxial digital cables are terminated with standard RCA connectors). But the cable itself is specially designed to handle the much wider frequency bandwidth of digital signals.

Component video jacks

This 3-cable connection allows the chrominance (color) and luminance (brightness) portions of a video signal to be processed separately. S-video works similarly, but component video improves color accuracy further by splitting the chrominance signal into two portions.

Component video jack Component video jacks
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Component video connector Component video connectors
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Component video connections are found on most DVD players and HDTV tuners, as well as on most TVs and A/V receivers. However, this type of connection can vary in bandwidth from unit to unit. To pass progressive-scan DVD signals without noticeable softening of the picture, a component video connection should have a bandwidth of 12 MHz or higher; passing HDTV signals without softening requires a bandwidth of 30MHz or higher. If you are only slightly shy of the required bandwidth for the signal you're viewing and your TV is 36" or less, the picture softening may be extremely subtle, or even unnoticeable.

Composite video jack

A composite video input or output uses a single standard RCA-style jack to pass video signals. This type of connection combines chrominance and luminance information, sending it along a single cable. Though capable of delivering a high-quality picture, composite video is not as accurate as either S-video or component video, both of which provide separate paths for chrominance and luminance.

Composite video jack Composite video jack
Composite video connector Composite video connector

Commonly found on A/V components like DVD players, VCRs, TVs, DBS systems, etc., composite video jacks are often grouped with corresponding stereo audio jacks (the composite video jack is usually yellow). Though they use standard RCA-type connectors, composite video cables are specially designed to maximize video signal transfer.


DVI (Digital Visual Interface) jack

DVI is a multi-pin connection used for passing standard-definition and high-definition digital video signals, found on some HDTV tuners, DVD players, HDTV televisions, and some computer displays. DVI connections transfer video signals in pure digital form, which is especially beneficial if you're using a "fixed-pixel" display (like a plasma, LCD, or DLP TV). Signals are encrypted with HDCP (High-bandwidth Digital Content Protection) to prevent recording.

DVI output jack DVI jack
DVI connector DVI connectorv

There are different kinds of DVI connections. DVI-D, which is the type of DVI connection found on most home video gear, carries digital-only signals. DVI-I, used with some computer video cards, is capable of passing both digital and analog video signals. Some TVs feature DVI-I inputs for greater hookup flexibility.


Ethernet jack

10/100 Base-T Ethernet card 10/100 Base-T Ethernet card
Ethernet connector Ethernet connector

The most popular form of Network Interface Card (NIC) available, Ethernet jacks allow PCs to interface with one another over home networks and broadband Internet connections. The very popular 10/100 Base-T Ethernet card — now a standard inclusion on many new PCs — allows transmission speeds of either 10 Mbps (megabits per second) or 100 Mbps, automatically self-adjusting to the proper speed for the type of connection being made.



Game/MIDI port

Game/MIDI jack Game/MIDI jack
Game/MIDI connector Game/MIDI connector

MIDI stands for Musical Instruments Digital Interface. The MIDI protocol lets PCs and electronic musical instruments (like digital keyboards and sequencers) share performance data with each other. This type of port is also frequently used to connect a joystick controller for PC games.


HDMI (High-Definition Multimedia Interface) jack

HDMI is a multi-pin connection used for passing standard- and high-definition digital video signals, as well as multi-channel digital audio, through a single cable. These connections can be found on nearly all current HDTVs, Blu-ray players, many DVD players, and home theater receivers. HDMI cable accommodates up to 5 Gbps bandwidth, so it can simultaneously transfer pure digital video and audio signals without compression (even HD video).

HDMI_output_jack HDMI jack
HDMI_output_jack HDMI Plug
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HDMI works especially well with a "fixed-pixel" display (like a plasma, LCD, or DLP TV), and is backwards-compatible with most DVI connections. Signals are encrypted with HDCP (High-bandwidth Digital Content Protection) to prevent recording.

HDMI can carry up to 8 discrete audio channels, making it forward-compatible with 7.1 sound systems. That means you can pass digital video and multi-channel audio signals between newer HDMI-equipped components along a single cable. Just be aware that HDMI is a developing standard, and so not all components that take HDMI have all the same features. Be sure to check out your component's owner's manual for HDMI compatibility. You can find out more in our article on the ins and outs of HDMI.

Minijack mono connector Headphone jack (mono) connector
Minijack stereo connector Headphone jack (stereo) connector
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Minijack Headphone jack
Headphone jack

Most portable CD players, MD recorders, and computer sound cards use headphone jacks for their analog audio inputs and outputs. Portable players usually output sound via a single headphone jack. Portable recorders usually add 2 additional jacks: a line input and a microphone input.

PC sound cards typically have at least 1 headphone jack line output; some also have a separate output. Like portable recorders, most sound cards also feature jacks for line input and mic input (these permit you to record sound directly to your hard disk drive).

Most headphone jack connections are stereo; that is, they pass both a left and a right audio channel. However, some headphone jack connections (such as microphone inputs) pass just a single mono audio channel. You can tell by looking at the number of rings on the plug: two for stereo and one for mono.


i.LINK port

i.LINK, also known as IEEE 1394 or FireWire®, is an extremely fast (up to 400 megabits per second), two-way digital connection used between older computers and peripherals, like Digital8 and Mini DV camcorders. It is used in digital camcorders because it is one of the few connections capable of quickly transferring full-motion video. Most consumer video equipment uses 4-pin i.LINK ports and connectors, but some peripherals employ a 6-pin i.LINK configuration — the additional two pins permit power to be fed to a device.

4-pin i.LINK port 4-pin i.LINK port
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6-pin i.LINK port 6-pin i.LINK port
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4-pin i.LINK connector 4-pin i.LINK connector
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6-pin i.LINK connector 6-pin i.LINK connector
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Mini-optical jack

This type of jack is commonly used for the digital audio input and output of portable audio devices. A mini-optical jack is the same shape and size as a standard analog audio minijack. This allows portable MiniDisc recorders to use a single input jack that accepts both mini-optical connectors and standard analog audio minijacks. The MD portable detects whether you're making a digital or an analog connection based on the type of cable you're using, and automatically selects the appropriate recording mode.

Mini-optical jack Mini-optical jack
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Mini-optical connector Mini-optical connector
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Optical digital jack (Toslink)

This type of jack is commonly used for the digital audio inputs and outputs on home A/V components such as receivers, CD players, full-sized MD recording decks, DVD players, and more. Also, some higher-end PC sound cards offer digital input and output using Toslink jacks.

Toslink jacks and connectors usually come with protective caps which need to be removed before connections are made.

Optical jack Optical jack
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Optical connector Optical connector
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Parallel port

The parallel port is one of the oldest PC-peripheral connection technologies still in existence. As such, it's significantly slower than many of the connection types that have followed in its wake — particularly USB and i.LINK — and its popularity has declined correspondingly. The parallel port most often takes a 25-pin connector, and in years past was very commonly used to connect printers and other external devices to PCs.

Parallel port Parallel port
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Parallel connector Parallel connector
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PCI slot

PCI is an acronym for Peripheral Component Interconnect. As the name implies, this is a slot that allows you to connect various peripheral devices to your PC, such as Ethernet cards, sound cards, and TV tuner cards. The slots themselves can only be accessed by opening your computer's case, so they're not designed to support the frequent peripheral-swapping you can do with connection technologies like USB and i.LINK.

Phono (turntable) input

When a turntable plays a vinyl record, it produces an audio signal that's considerably different from the standard line-level signal output by CD players, tape decks, and other components. Not only is the phono signal much lower in voltage, but the process of vinyl mastering involves applying a special equalization curve that cuts low frequencies and boosts highs. (This prevents the "overcutting" of grooves, and minimizes noise.)

Some receivers feature a specialized phono input intended for turntables only. The signal coming from this input is sent to a dedicated preamp circuit which applies inverse equalization and boosts the signal up to the standard line level — resulting in proper sound from your turntable. (Keep in mind that feeding an ordinary line-level signal into your receiver's phono input will probably result in horrific distortion, and could actually damage your amplifier and speakers.)

Receivers with a phono input also feature a ground screw for connecting your turntable's ground wire. (Neglecting this connection can result in an audible hum from your system.) If your receiver or preamplifier doesn't have a specialized phono input, you can use an in-line phono preamp, which allows you to connect your turntable any regular line-level input.

Phono input Phono inputs

PS/2 keyboard port

The keyboard port (a 6-pin configuration) was commonly used by Windows®-based PCs, but now the USB port is far more common. Some CD mega changers with memory for disc and song titles also feature their own PS/2 jack — this allows you to plug in a keyboard for speedy naming of your CDs. Additionally, some older PC-friendly peripherals can Y-jack into a PS/2 port as a source of power.

PS/2 keyboard port PS/2 keyboard port
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PS/2 keyboard connector PS/2 keyboard connector
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RGB (D-sub 15-pin) jack

Found on some HDTV-ready TVs and HDTV tuner boxes, RGB connections are used for transferring video signals, including high-definition content. As implied by its name, RGB sends the red, green, and blue components of the video signal along separate paths.

Though RGB connections can take a number of forms, one that's increasingly common on TVs and set-top boxes is the D-sub 15-pin jack. If you own a computer, D-sub 15-pin connections may look familiar — they're the same ones found on standard VGA-type computer monitors. RGB connections pass video signals in the analog domain.

RGB (D-sub 15-pin) output jack RGB (D-sub 15-pin) output jack
RGB (D-sub 15-pin) connector RGB (D-sub 15-pin) connector

RJ-11 and RJ-14 phone/modem jacks

Modems, receivers, DVRs, and other kinds of A/V gear use these jacks for sending and receiving information via a telephone line. Usually computer modems feature a second phone jack — this allows you to plug in a telephone that will be operational whenever the modem is not in use.

RJ-11 jacks and connectors allow for the transmission of a single phone line; RJ-14 connections can carry two separate phone lines simultaneously. The connectors for one type will fit into the jacks of the other, but if you plug an RJ-14 cable into an RJ-11 jack, you'll lose the ability to access the second line from the computer and/or phone thus connected.

RJ-11 phone/modem jack RJ-11 phone/modem jack
RJ-11 phone/modem connector RJ-11 phone/modem connector


Serial (RS-232C) port

A serial port, or RS-232C port, is an interface that provides low-speed communication between your PC and attached devices (such as digital cameras, printers, and more). Because it is so slow in comparison to newer connections (like USB or i.LINK), fewer and fewer peripherals offer serial connections, and new PCs tend to provide only one serial port, if any. Serial ports most frequently take a 9-pin connector, although a number of older peripherals employ 25-pin serial ports.

Serial port Serial port
Serial connector Serial connector

Speaker wire (no connector)

Speaker wire consists of two leads, typically encased and bundled in plastic insulation — one for the positive signal, and one for the negative. Usually, speaker wire is marked (+) and (-) to help you distinguish between the two.

Though it's not an ideal long-term installation method, you can connect your speakers and receiver using just the bare, stripped ends of your speaker wire. Drawbacks to this approach include:

  • Stray wire strands, if not properly twisted, could make contact with the cable's other lead, and cause a potentially harmful short circuit.
  • Bare wire ends corrode, since they're made of copper. Most speaker wire connectors, on the other hand are usually coated with a corrosion-free material, such as gold.
Speaker wire Speaker wire

Speaker wire connectors

All kinds of speaker wire connectors are designed to accomplish the same job: to make solid electrical contact between your speaker wire and your gear. By using speaker wire connectors, you reduce the risk of a short circuit caused by frayed wire strands. And since speaker wire connectors usually have corrosion-free contacts, they help maintain optimum connection over the long term.

There are 4 main kinds of speaker wire connectors:

  • Pins. Pin connectors may either be straight or angled. They work with spring clip speaker terminals, as well as with binding posts.
  • Spades. Spade connectors feature a forked piece of metal, designed to hug the collar of a 5-way binding post terminal. The spade is then secured by tightening the binding post's cap. Spade connectors give you very secure contact.
  • Banana plugs. If you have binding post terminals on your speakers and/or receiver, banana plugs are a great choice. The flexible metal collar of a banana plug is slightly wider than the center hole of a binding post. It compresses to fit when you plug it in, resulting in a very solid connection. Banana plugs are extremely quick and easy to hook up.
  • Double-banana plugs. The same as banana plugs, except the positive and negative banana connectors are both fixed in a molded housing that spaces them 3/4" apart. (These are even quicker and easier to connect than regular, single banana plugs — as long as the terminals on your speakers and/or receiver are true 5-way binding posts with the proper spacing.)
Pin connector Pin connector
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Banana plug Banana plug
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Double banana plug Double banana plug
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Spring clip speaker terminals

Spring clip terminals are a type of connection used for amplified, speaker-level signals, usually found on lower-priced speakers and lower- to medium-priced receivers. Spring clips accept bare speaker wire, as well as pin-type speaker wire connectors. To make the connection, just push the spring-loaded lever, insert the wire (or connector), and release. Spring clips are sometimes also referred to as "push terminals."

Each speaker (or each output channel on a receiver) uses a pair of spring clips for a single connection: a red one for the positive speaker lead, and a black one for the negative lead.

Spring clip speaker terminals Spring clip speaker terminals
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Stereo RCA jacks

RCA connections are the standard means of passing analog line-level (or "preamp-level") audio signals between components. RCA jacks are commonly found on most types of A/V gear: receivers, CD players, turntables, MiniDisc recorders, cassette decks, VCRs, DVD players, and more.

The audio inputs and A/V inputs found on receivers are RCA connections (though some A/V inputs may also include a different type of jack — such as HDMI or component video — for the "video" portion of the signal).

Usually, RCA jacks, connectors and cables are grouped in stereo pairs, with one connection for the left audio channel and one for the right. However, some components (such as many powered subwoofers) use a single mono RCA jack for audio input and/or output.

(Note that a turntable's RCA jacks output a signal that's significantly different from standard line-level signals; hookup requires a specially designed phono input or an in-line phono preamp.)

Stereo RCA jacks Stereo RCA jacks
Stereo RCA connectors Stereo RCA connectors

S-video jack

Found on DVD players, DBS receivers, Super VHS VCRs, TVs, and other kinds of A/V gear, S-video inputs and outputs use a round, 4-pin jack used to pass video signals. The "S" in S-video stands for "separate": S-video connections transmit the chrominance (color) and luminance (brightness) portions of a video signal along different paths, allowing them to be processed separately.

S-video provides a sharper picture than composite video. However, component video connections yield even better performance than S-video by further dividing the chrominance portion of the video signal.

S-video jack S-video jack
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S-video connector S-video connector
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USB port

USB (Universal Serial Bus) is a "plug and play" interface between a computer and peripherals (like audio players, camcorders, digital cameras, keyboards, and printers). USB's speed makes it ideal for music and digital image transfer. The newest USB 2.0 standard transfers information at a fast 480 Mbps. That kind of speed makes USB 2.0 suitable for transferring demanding files like full-motion video and high-resolution photos. Most USB 2.0 devices are backwards-compatible with older USB 1.1 devices.

USB ports are expandable with the addition of hubs, which allow you to connect several peripherals simultaneously through a single USB port. There are several types of USB connectors. The USB Type A connector plugs into the USB port on your computer. The USB Type B connector plugs into a peripheral device (such as a monitor or printer). Some compact devices like cameras and USB audio adapters feature smaller USB jacks, either mini USB or mini USB version 2. These devices typically include a Type A-to-mini-USB cable.

USB port (Type A) USB port (Type A)
USB connector (Type A) USB connector (Type A)
Mini USB port Mini USB port
Mini USB connector Mini USB connector


VGA (Video Graphics Array) connector

While used primarily for computer monitors, VGA cables also connect to  flat-panel LCD and plasma TVs to display video from a computer. This 15-pin connector — usually called a "PC input" on a TV — carries analog video information, as opposed to digital connections like HDMI.

VGA input VGA input
VGA connector VGA connector



XLR connector

Originally designed for professional audio use, XLR audio cable is used primarily with high-performance audio gear. The connector has three pins — a positive conductor, a negative conductor, and a ground. The ground wire helps reduce electronic noise throughout the cable. A clasp built into the round XLR plug locks it tightly into the socket, ensuring a secure connection.

XLR cables are also used with microphones requiring "phantom power." An electrical charge runs through the ground wire, powering the microphone's internal pre-amps and allowing it to function.

XLR connector XLR connector
XLR input XLR input



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Last updated May 20, 2016
  • gary from palm coast,fl

    Posted on 7/26/2015 4:01:59 PM

    excellent how you explain each item. thank you