BNC

There is also a twinax version of this that has a 2-wire twisted pair with a shield around it used for high speed data applications. You can tell the difference by the number of bayonets. Coax has 2, twinax has 3.

DA-15 (DB-15)

DB-25

DC-37 (DB-37)

D subminiature, 37 pin. Many different types of applications.

DD-50 (DB-50)

D subminiature, 50 pin. Many different types of applications. Some of the common pinouts are shown below.

DE-9 (DB-9)

DS0

The basic voice channel of a North American Telephone Data Multiplexed (TDM) Plain Switched Telephone Network (PSTN). It occupies 64 kbps of the TDM channel capacity.

HDB-15

High Density DB-15 connector.

Modular

4 pin

8 pin

RJ-11

This is your typical telephone jack. If it goes between the wall outlet and the phone it is a RJ-11. If it goes between the phone and the handset, it is a smaller version called an RJ-11C. (See modular, 4 pin)

RJ-45

This is an 8 pin modular jack used in ethernet and ISDN applications. It is also used in telephone applications for T1 and DS0 applications. Pinouts for T1 and DS0 differ from ethernet, ISDN and each other so they cannot be accidentally cross connected. Also, Cisco has a version that is RS-232 signaling in a 8-pin modular plug. (See modular, 8 pin)

T1

A North American Telephone Data Multiplexed signal consisting of 24 voice channels that are transmitted at 1.544 Mbps.

TNC

Threaded Naval Connector. This is the same as a BNC except it used threaded connector instead of the bayonet.