The University of Texas at Austin
As part of the Web Central Services Retirement project, the ITS website will be retired. Information about IT services will be replaced by two new sites, IT@UT and UT ServiceNow, and ITS departmental information will be migrated to a new location. All changes will be completed by 7/28/2016.

Telephone Service (Retirement in Progress)

General Information: Telephone Diagrams & Terms

Shown below is a diagram of a single-line telephone. The terms listed provide information about the physical features of the telephone set and tones or signals received from the system, and can help when describing telephone troubles.

Diagram of a Telephone

Dial: Rotating disk or push-button assembly used for entering digits and accessing features.

Direct-In-Dial: A telephone number which rings directly at a person's desk; the call does not go through an operator or receptionist. (See also Private Branch Exchange below).

Handset: The portion of the telephone containing the transmitter and receiver which is hand held when the telephone is in use.

Handset Cord: The coiled connection between the handset and the base of the telephone.

Hookflash: The process of pressing the switchhook down for one-half second and releasing. The Hookflash is used to access system features. (Refer to Introduction above for further information about hookflash.)

Hunt Group: A series of telephones or telephone numbers on multi-button or single-line phones, which search for a free line when the main number is called. If the first line is busy, the call will ring at the next available line. Members of a hunt group are often referred to as terminals or "terms" of the main number.

Key Telephone System: Electronic (EKS) or electromechanical (KS) telephone system allowing several users access to the same lines. Telephone instruments are usually multi-button (line) sets with a hold button and internal intercom features.

Mounting cord: The connection between the base of the telephone and the wall or floor.

On-hook: The handset is in the cradle.

Off-hook: You are talking, the handset is in your hand.

Private Branch Exchange (PBX): Local departmental automatic telephone system providing internal features and connection of extensions as well as access to the UT campus and public network. (See also Direct-in-Dial, above.)

Receiver: The earpiece or portion of the handset through which you hear the other party's voice.

Station Number: The last five-digits of an on-campus phone number. (Also used to refer to a two- or three-digit intercom number or a three-digit PBX extension.)

Switchhook: A device in the cradle, on the side, or on the top of the telephone which signals the status of the telephone to the switching equipment; on-hook (not in use), or off-hook (in use).

Transmitter: The portion of the handset into which you speak.


  • Dialing 71 on a rotary dial telephone is equivalent to the * on a tone dial telephone.

  • Dialing # after some phone numbers or a speed call number will speed up the completion of that call. There is no rotary dial equivalent for a #.

  • Features are activated by either a two-digit code xx or an asterisk followed by a two-digit code *xx. Be sure to note the difference when attempting new features.

Last updated April 10, 2012 @ 1:44 pm

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