There are many types of connectors used to connect electronic circuits to each other and the outside world. Some of the most common are shown below.

Fahnestock Clip

Fahnestock clip
Banana Plugs
Banana plugs
Dual Banana Plug
Dual banana plug

The Fahnestock clip is mostly obsolete but is still used in classrooms for demonstration circuits. Banana plugs are still widely used.

RCA Plugs
RCA (phono) plugs

RCA Jacks
RCA (phono) jacks
Phone Plugs and Jacks
Phone plugs and jacks

Subminiature stereo (bottom), miniature mono and stereo (above).

RCA connectors are sometimes called phono connectors because they were commonly used to connect phonograph turntables to amplifiers. RCA connectors typically connect to shielded cable (the center conductor surrounded by a cylindrical shield conductor). A disadvantage of the RCA connector is that the center conductor makes contact before the outer conductor. Without the outer shield connected, noise, often a lot of it, enters the circuit for the short time before the outer conductor is connected. In audio systems, this causes a loud buzzing in the speakers. Phono connectors are not to be confused with phone connectors, which were widely used for telephone exchange switchboards (1/4-inch standard version). Many phone jacks have built-in switches that switch a circuit to the plug. For example, with the plug out sound signals go to a speaker. When the plug is inserted into the jack, the speaker is automatically disconnected and the signal is routed to the headphones through the phone plug.

Alligator Clips

Alligator (crocodile) clips
DIN Connector
DIN (Deutsches Institut für Normung) connector
BNC Banana
Combination binding post, banana jack and BNC adapter

The right image above has binding posts (wires are threaded through the holes then the knobs are tightened onto the wires). The binding posts are also banana jacks and can accept banana plugs in the ends. The holes in the side of the adapter also accept banana plugs. All this adapts to a BNC connector.


BNC connector

D-sub, D-type or D-shell connector
Blade Connectors
Blade connectors

The BNC connector (Bayonet Neill-Concelman) is named for its designers, Paul Neill (Bell Laboratories) and Carl Concelman (Amphenol). It is a shielded connector like the RCA connector but has a controlled characteristic impedance (something you will learn about in communication circuits). It also has a locking “bayonet” mechanism. To disconnect it you have to push then turn it.

The D-sub connector is named for the shape that is similar to the letter “D.” It is mistakenly called a DB connector in some computer circles. Hewlett-Packard calls the 25-pin version the DB-25 and this was picked up in the computer industry. HP calls no other version of the D-sub connector a “DB” connector.

Blade connectors come in several styles such as spade lugs (flat or forked), bullet lugs and ring lugs.

Coaxial Power Connector

Coaxial power connector

Molex Amp

Molex (Amp) connector
Edge Connector
Edge connector

Coaxial power connectors come in various sizes that are incompatible with each other. Connectors for higher voltages are often chosen so that they cannot be plugged in to lower voltage devices.

The Molex connector (four-pin version shown) was patented in the 1960s. The similar, but incompatible AMP connector is usually called a Molex connector by mistake. Each pin or receiver is crimped to an individual wire then inserted into the connector shell where it snaps into place. The AMP connector was the power connector of choice for hard disk drives in computers for many years (and always called a Molex connector).


BNC stands for British Naval Connector, Bayonet Nut Connector, Berkeley Nucleonics Corporation or some other nonsense.

I originally didn't believe it stood for “Bayonet Neill-Concelman” either. However, the Amphenol catalog confirms the name.[1]

D-sub connectors are called DB-9M (9-pin male), DB-25F (25-pin female), etc.

Actually, these names have been used in the computer industry for so long that they are leaking into the electronics industry. The original names used by Hewlett-Packard are DA-15, DB-25, DC-37, DE-50 and DE-9. The number indicates the number of pins. In electronics, these connectors are usually just called D-sub, D-type or D-shell connectors. However, the names commonly used in the computer industry, such as DB-15M for the 15-pin male and DB-9F for 9-pin female, are making inroads into the electronics industry lexicon.


1https://web.archive.org/web/20101128210217/www.amphenol.com/pdfs/AmphenolCatFinal.pdf  (page 31)