Reorder tone
Encyclopedia
The reorder tone, also known as the fast busy tone, is the congestion tone or all trunks busy (ATB) tone of a public switched telephone network
. It varies from country to country; in the USA it is a dual-frequency
tone of 480 Hz and 620 Hz at a cadence of 0.25 second
s on, 0.25 off; that is two beeps per second. It is used to indicate that an invalid code has been dialled, or that all circuits (trunks) are busy and/or the call is unroutable. A PBX will often also do this for an invalid extension
, while an invalid telephone number
on the PSTN usually gets the triple special information tone
and a recording. Reorder tone is sometimes confused with the busy signal
.
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
. It varies from country to country; in the USA it is a dual-frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
tone of 480 Hz and 620 Hz at a cadence of 0.25 second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
s on, 0.25 off; that is two beeps per second. It is used to indicate that an invalid code has been dialled, or that all circuits (trunks) are busy and/or the call is unroutable. A PBX will often also do this for an invalid extension
Extension (telephone)
An extension telephone is an additional telephone wired to the same telephone line as another. In middle 20th century telephone jargon, the first telephone on a line was a "Main Station" and subsequent ones "Extensions". Such extension phones allow making or receiving calls in different rooms,...
, while an invalid telephone number
Telephone number
A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given orally to a switchboard operator...
on the PSTN usually gets the triple special information tone
Special information tone
In telephony, a special information tone is an international standard three beep signal indicating a call did not go through and usually precedes a recorded announcement explaining the problem...
and a recording. Reorder tone is sometimes confused with the busy signal
Busy signal
A busy signal in telephony is an audible or visual signal to the calling party that indicates failure to complete the requested connection of that particular telephone call....
.