Dial tonewikipedia
A dial tone is a telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone, when an off-hook condition is detected.
dial tonedial-tonestutter dial tonetonedialling tone

Telephone exchange

telephone exchangeexchangescentral office
A dial tone is a telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone, when an off-hook condition is detected.
Central office locations may also be identified in North America as wire centers, designating a facility from which a telephone obtains dial tone.

Special information tone

special information tonespecial information tonesOOS
If no digits are forthcoming, the permanent signal procedure is invoked, often eliciting a special information tone and an intercept message, followed by the off-hook tone, requiring the caller to hang up and redial.
Like a dial tone or busy signal, the SIT is an in-band signal intended both to be heard by the caller, and to be detected by automated dialing equipment to determine a call failed.

Telephone call

telephone callcallphone call
It indicates that the exchange is working and is ready to initiate a telephone call.
Otherwise, the calling party is usually given a tone to indicate they should begin dialing the desired number.

Off-hook tone

off-hook tonehigh toneHowler/off-hook warning
If no digits are forthcoming, the permanent signal procedure is invoked, often eliciting a special information tone and an intercept message, followed by the off-hook tone, requiring the caller to hang up and redial.
It is played between the dial tone timeout recording ("If you would like to make a call...") and the permanent signal holding state.

Call forwarding

call forwardingforwardingGSM forwarding standard features codes
It may serve as a message-waiting indicator for voice mail, or indicate that a calling feature, such as call forwarding has been activated.
More consistently, the forwarded line indicates its condition by stutter dial tone.

Message-waiting indicator

message-waiting indicatorMessage waiting indicationsMessage Waiting Indication
It may serve as a message-waiting indicator for voice mail, or indicate that a calling feature, such as call forwarding has been activated.
VMWI differs from existing features that use other message indicators, such as audible stuttered dial tone, in that it activates a visual indicator on the CPE.

Precise Tone Plan

The Precise Tone Plan for the North American Numbering Plan of the US, Canada, and various Caribbean nations specifies a combination of two tones (350 Hz and 440 Hz) which, when mixed, appear to have a modulation at 90 Hz. The UK's dial tone is extremely similar, but combines two 350 Hz and 450 Hz tones instead.

9-1-1

9-1-1911911 call
It is maintained only so that an attached phone can dial the emergency telephone number (such as 911, 112 or 999), in compliance with the law in most places.
On wired (land line) phones, this usually is accomplished by a "soft" dial tone, which sounds normal but will allow only emergency calls (or, in some cases, will state the number of the local telephone company which may be called in order to initiate regular service.) Often, an unused and unpublished phone number will be issued to the line so that it will work properly.

Busy signal

busy signalengaged tonebusy
In some phone companies in the United Kingdom, the busy signal is played after the dial tone to indicate the caller has used up their allocated time to dial a number and must hang up, before the off-hook tone is played.

Rotary dial

rotary dialdialrotary telephone
When he picked up his own household phone his assistant had to explain what the strange noise was, as well as show Eisenhower how to use a rotary dial phone.

Naked DSL

naked DSL
A naked DSL (a.k.a. standalone or dry loop DSL) is a digital subscriber line (DSL) without a PSTN (analogue telephony) service — or the associated dial tone.

Out-of-band infrastructure

out-of-band infrastructure
Having a critical requirement to always provide dial-tone for health and safety reasons, the telecom industry created elaborate mechanisms which allowed quick service restoration using alternative communication pathways which were physically and logically separate from the voice traffic itself.

Feature interaction problem

feature interactionProduct featuresinteractions
The originating features may in turn include the provide dial tone feature, digit collection feature and so on.

Class-5 telephone switch

Class 5end officeClass 5 switch
Class-5 switch services include basic dial-tone, calling features, and additional digital and data services to subscribers connected to a local loop.

Dry loop

dry loopalarm circuitdry pair
The pair does not provide dial tone or battery (continuous electric potential), as opposed to a wet pair, a line usually without dial tone but with battery.

Call waiting

call waitingcall-waiting
A stutter dial tone confirms the de-activation.

Dial Tone (disambiguation)

dial tone is a tone on a phone indicating that the line is operational

Ground start

ground startused to request an external connection
In telephony, ground start is a method of signaling from a terminal of a subscriber local loop to a telephone exchange, where one side of a cable pair is temporarily grounded to request dial tone.

Network effect

network effectnetwork effectsnetwork externalities
In practical terms, each additional user increases the total system load, leading to busy signals, the inability to get a dial tone, and poor customer support.

Telephone

telephonephonetelephones
The exchange detects this current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness.

E.123

Microsoft's canonical address format
A tilde indicates an additional dial tone that the user should wait for.

Number One Crossbar Switching System

1XBNo. 1 Crossbar1XB switch
As in the panel switch, the sender then found the chosen junctor and supplied dial tone.