A lineman's handset is a special type of telephone

Telephone

The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...

 used by technicians for installing and testing local loop

Local loop

In telephony, the local loop is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the carrier or telecommunications service provider's network...

 telephone line

Telephone line

A telephone line or telephone circuit is a single-user circuit on a telephone communication system...

s. It is also called a test set, butt set, or buttinski.

Components

A typical lineman's handset integrates an earpiece, a mouthpiece, a dialing interface, and a set of test leads for connecting to the telephone circuit. Originally, lineman's handsets featured a rotary dial

Rotary dial

The rotary dial is a device mounted on or in a telephone or switchboard that is designed to send electrical pulses, known as pulse dialing, corresponding to the number dialed. The early form of the rotary dial used lugs on a finger plate instead of holes. Almon Brown Strowger filed the first patent...

, but modern sets use some variant of the standard 12-button DTMF

Dual-tone multi-frequency

Dual-tone multi-frequency signaling is used for telecommunication signaling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching center. The version of DTMF that is used in push-button telephones for tone dialing is...

 keypad

Telephone keypad

A telephone keypad is a keypad that appears on a "Touch Tone" telephone. It was standardised when the dual-tone multi-frequency system in the new push-button telephone was introduced in the 1960s, which gradually replaced the rotary dial....

. Most handsets are designed to be used with analog "POTS

Plain old telephone service

Plain old telephone service is the voice-grade telephone service that remains the basic form of residential and small business service connection to the telephone network in many parts of the world....

" lines, and have limited or no function with digital circuits.

In addition to the basic features listed above, handsets often include one or more of:

• Speakerphone
  Speakerphone
  A speakerphone is a telephone with a microphone and loudspeaker provided separately from those in the handset. This device allows multiple persons to participate in a conversation...
  
  
• Redial
• A talk/monitor toggle switch
• Mute
• Hook flash
  Hook Flash
  Hook flash or flash is a button on a telephone that simulates quickly hanging up then picking up again . This action can signal the telephone exchange to do something. A common use of hook flash is to switch to another incoming call with the call waiting service...
  
   button
• Tone/pulse dialing
  Pulse dialing
  Pulse dialing, dial pulse, or loop disconnect dialing, also called rotary or decadic dialling in the United Kingdom , is pulsing in which a direct-current pulse train is produced by interrupting a steady signal according to a fixed or formatted code for each digit and at a standard pulse repetition...
  
   selection switch
• Low-pass filter
  Low-pass filter
  A low-pass filter is an electronic filter that passes low-frequency signals but attenuates signals with frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a high-cut filter, or treble cut filter...
  
  ing to prevent disruption of data communications (such as DSL)
• A mechanical hook for hanging the set from a tool belt. On some sets, it may be moved to the receiver side, mouthpiece side, or removed altogether.

Typical use

A lineman's handset typically connects via a pair test leads, not the modular connector

Modular connector

Modular connector is the name given to a family of electrical connectors originally used in telephone wiring and now used for many other purposes. Many applications that originally used a bulkier, more expensive connector have now migrated to modular connectors...

 found on most consumer telephone equipment. The test leads will feature some combination of alligator clips (to connect to bare wires), a piercing spike or "bed-of-nails" (for insulated wires), and something designed to fit a punch block

Punch block

A punch down block is a type of electrical connection often used in telephony. It is named because the solid copper wires are "punched down" into short open-ended slots which are a type of insulation-displacement connectors...

. Adapter

Adapter

An adapter or adaptor is a person that adapts or a device that converts attributes of one device or system to those of an otherwise incompatible device or system.Some adapters may only affect physical attributes:...

s designed to fit other punch block types, heat coil

Heat coil

Heat coils, also known as protectors, bugs or carbons serve as a surge protector between the telephone exchange and outside plant. They are commonly the last point of appearance for a telephone circuit before it leaves the office, for example on the outside plant side of the main distribution frame...

 sockets, or modular jacks may also be used.

A butt set can be connected wherever there is a line appearance

Point of appearance

Point of appearance is a generic term for any point in a telephone/data circuit from which a technician can test or pull stats. Some appearances are virtual, such as a Digital cross connect system computer terminal. Others are physical, like a punch down COSMIC frame where a technician can place a...

 -- anywhere the wires are accessible. Inside the central office

Telephone exchange

In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...

, this would be at a main

Main distribution frame

In telephony, a main distribution frame is a signal distribution frame for connecting equipment to cables and subscriber carrier equipment . The MDF is a termination point within the local telephone exchange where exchange equipment and terminations of local loops are connected by jumper wires...

 or intermediate

Intermediate distribution frame

Intermediate distribution frame : In a central office or customer premises, a frame that cross-connects the user cable media to individual user line circuits and may serve as a distribution point for multipair cables from the main distribution frame or combined distribution frame to individual...

 distribution frame

Distribution frame

In telecommunications, a distribution frame is a passive device which terminates cables, allowing arbitrary interconnections to be made.For example, the Main Distribution Frame located at a telephone central office terminates the cables leading to subscribers on the one hand, and cables leading to...

. For outside plant

Outside plant

In telecommunication, the term outside plant has the following meanings:*In civilian telecommunications, outside plant refers to all of the physical cabling and supporting infrastructure , and any associated hardware located between a demarcation point in a switching facility and a demarcation...

, this would include any serving area interface

Serving area interface

The serving area interface or service area interface often called B-box, cross-connect box, cross box, ped , or access point is an outdoor telecommunications cabinet usually mounted on the ground on cable right-of-ways, but sometimes also on telephone poles...

, such as a cross-connect box or aerial splice enclosure. At subscriber site (e.g., residence), this could be inside or behind the housing of a modular connector, or at the network interface

Network interface device

In telecommunications, a Network Interface Device is a device that serves as the demarcation point between the carrier's local loop and the customer's premises wiring....

.

When connected to a line, a lineman's handset is essentially indistinguishable from regular subscriber equipment. The technician can monitor an active call, answer incoming calls, and/or make outgoing calls. Common tests include checking for dial tone

Dial tone

A dial tone is a telephony signal used to indicate that the telephone exchange is working, has recognized an off-hook, and is ready to accept a call. The tone stops when the first numeral is dialed...

, using ANAC

Automatic number announcement circuit

An automatic number announcement circuit is a special telephone number that is meant to be used by phone company technicians and other telecommunications technicians to determine the phone number of a particular line....

 to identify the line, and using a ringback number

Ringback number

Ringback number is a number used by many telephone company linemen/technicians to test whether or not a new telephone line installation is working correctly and the phone number is routing properly....

.