Ringing (telephony)

Last updated

Ringing is a telecommunication signal that causes a bell or other device to alert a telephone subscriber to an incoming telephone call. Historically, this entailed sending a high-voltage alternating current over the telephone line to a customer station which contained an electromagnetic bell. It is therefore also commonly referred to as power ringing, to distinguish it from another signal, audible ringing, or ringing tone, which is sent to the originating caller to indicate that the destination telephone is in fact ringing. [1] [2]

Contents

Specifications

In landline telephones, bells or ringtones are rung by impressing a 60 to 105-volt RMS 20-Hertz sine wave across the tip and ring conductors of the subscriber line, in series with the (typically) −48 VDC loop supply. [3] This signal is produced by a ringing generator at the central office.

When the switching system directs a call to a particular subscriber line, a relay on the line card connects the ringing generator to the subscriber line. The exchange also sends a ringing tone to the calling party. When the called party answers by taking the telephone handset off the switchhook, the subscriber's telephone draws direct current from the central office battery. This current is sensed by the line card and the ringing relay is de-energized.

Multi-party lines

On multi-party lines, ringers would typically be connected from one side of the two-wire line to ground; a "tip party" and "ring party" would have bells connected from opposite sides of the line. On a two-party service, each user would not hear ringing for calls to the other party. Some 20th-century independent telephone companies deployed four-party lines which used differing frequencies for selective ringing of individual parties (the four possible combinations were 20 Hz or 30 Hz from tip to ground, 20 Hz or 30 Hz from ring to ground). If additional parties were added to the same line, distinctive ringing patterns would need to be used to identify the called subscriber; these were audible to the multiple users on the line.

Ringing generator

A ring generator or ringing voltage generator is a device which outputs 20 cycle sinusoidal AC at up to 110 volts peak to power bells or annunciators in one or more telephone extensions. [4] The output stops if a handset is taken off the hook.

In terminology devised by phone phreaks, a ringing generator is a magenta box. The device can be used to simulate an incoming call by applying the AC ringing signal voltage to a POTS line to make the telephones on that line ring. A magenta box in conjunction with an orange box (which emulates the caller ID signal to create falsified data) is called a vermilion box.

The hardware also has multiple legitimate applications. While a telephone exchange includes a central source of ringing voltage at the switchboard, a private branch exchange or telephone-based intercom must provide a local source of AC ringing voltage. Theatrical performances often deploy a ringing telephone on-stage as a stage prop. An analog telephone adapter for voice over IP applications has to provide its own ringing voltage generator and other line signaling services for standard telephone extensions. The hardware may also be useful to technicians for test purposes.

Stand-alone ringing voltage generators are commercially manufactured; [5] [6] ring generators are also pre-built for inclusion in other telecommunications equipment [7] and various circuits published by hobbyists to generate [8] [9] or detect [10] ringing voltage for analogue telephony.

A closed system, such as an intercom or private branch exchange, need not comply with standards for ringing if it does not use standards-compliant telephone extensions. Some office telephones replace the bells with separately-wired low-voltage DC buzzers or use entirely custom-designed extensions which only work with one manufacturer's switchboard. These avoid the need to generate 20 Hz 90V sinusoidal AC, but are not compatible with standard telephone ringers.

Ring forward and ringback

Ring forward is a brief signal of about 100 ms duration sent during an established connection on a trunk line between central offices by the calling operator to recall the operator at the receiving office. [1] If the trunk line is not metallic, an equivalent on-hook condition is sent that is converted at the receiving trunk equipment to a recall signal.

In contrast to ring forward, the ringback signal is originated from the receiving or called end of a trunk line during an established connection, to recall the originating operator. [1] The signal is also sent by a coin line operator to recall a customer at a pay station after the customer hangs up, for example to inform the customer of time and charges of the completed call.

See also

Related Research Articles

Telephone switchboard

Throughout the 20th century, telephone switchboards were devices used to connect circuits of telephones to establish telephone calls between users or other switchboards. The switchboard was an essential component of a manual telephone exchange, and was operated by switchboard operators who used electrical cords or switches to establish the connections.

Telephone Telecommunications device

A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from Greek: τῆλε and φωνή, together meaning distant voice. A common short form of the term is phone, which came into use almost immediately after the first patent was issued.

In telephony, ringdown is a method of signaling an operator in which telephone ringing current is sent over the line to operate a lamp or cause the operation of a self-locking relay known as a drop.

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. It indicates that the exchange is working and is ready to initiate a telephone call. The tone stops when the first dialed digit is recognized. If no digits are forthcoming, the partial dial 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.

Blue box Device for hacking telephone network

A blue box is an electronic device that produces tones used to generate the in-band signaling tones formerly used within the North American long-distance telephone network to send line status and called number information over voice circuits. This allowed the user, referred to as a "phreaker", to surreptitiously place long-distance calls that would be billed to another number or dismissed entirely as an incomplete call. A number of similar "color boxes" were also created to control other aspects of the phone network.

A ringtone, ring tone or ring is the sound made by a telephone to indicate an incoming call. Originally referring to and made by the electromechanical striking of bells, the term now refers to any sound on any device alerting of a new incoming call—up to and including recordings of original telephone bells.

A ringback number is a telephone number for a telephone line that automatically calls the line that the call was placed from, after the caller has hung up. The typical use of this facility is by telephone company technicians for testing a new installation or for trouble-shooting.

Business telephone system Multiline telephone system typically used in business environments

A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system (KTS) to the private branch exchange (PBX).

In telecommunications, a long-distance call (U.S.) or trunk call is a telephone call made to a location outside a defined local calling area. Long-distance calls are typically charged a higher billing rate than local calls. The term is not necessarily synonymous with placing calls to another telephone area code.

An intercept message is a telephone recording informing the caller that the call cannot be completed, for any of a number of reasons ranging from local congestion, to disconnection of the destination phone, number dial errors or network trouble along the route.

Loop start is a telecommunications supervisory protocol between a central office or private branch exchange (PBX) and a subscriber telephone or other terminal for the purpose of starting and terminating a telephone call. It is the simplest of the telephone signaling systems, and uses the presence or absence of loop current to indicate the off-hook and on-hook loop states, respectively. It is used primarily for subscriber line signaling. An extension of the protocol that adds disconnect supervision is often called kewlstart.

Ringing tone is a signaling tone in telecommunication that is heard by the originator of a telephone call while the destination terminal is alerting the receiving party. Audible ringing is typically a repeated tone that is not necessarily synchronous with the cadence of the power ringing signal that is sent to the called party.

A party line is a local loop telephone circuit that is shared by multiple telephone service subscribers.

1A2 Key Telephone System Modular business telephone system

The 1A2 Key Telephone System is a business telephone system developed and distributed by the Western Electric Company for the Bell System.

Tip and ring Two conductors or sides of a telephone line

Tip and ring are the names of the two conductors or sides of a telephone line. The terms refer to the telephone plugs used for connecting telephone calls in manual switchboards. One side of the line is connected to the metal tip of the plug, and the second is connected to a metal ring behind the tip, separated and insulated from the tip by a non-conducting material. When inserted into a jack, the plug's tip conductor connects first, followed by the ring conductor. In many European countries, tip and ring are referred to as the A and B wires.

Telephone number Sequence of digits assigned to a telephone subscription

A telephone number is a sequence of digits assigned to a fixed-line telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices for data transmission via the public switched telephone network (PSTN) or other public and private networks.

A ringer box is a telephone signaling device, similar to a bell box. It usually contains an electromechanical gong and was used with most early desk stand telephones, such as candlestick telephones and the Western Electric type 102 and 202 telephones, which were too small to hold a ringer and other required electrical components. Many pay station telephones also used a separate ringer box.

Telephone exchange Interconnects telephones for calls

A telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital systems to establish telephone calls between subscribers.

Telephone magneto Hand-cranked electrical generator

A telephone magneto is a hand-cranked electrical generator that uses permanent magnets to produce alternating current from a rotating armature. In early telegraphy, magnetos were used to power instruments, while in telephony they were used to generate electrical current to drive electromechanical ringers in telephone sets and activate signals on operator consoles.

Panel switch

The Panel Machine Switching System is a type of automatic telephone exchange for urban service that was used in the Bell System in the United States for seven decades. The first semi-mechanical types of this design were installed in 1915 in Newark, New Jersey, and the last were retired in the same city in 1983.

References

  1. 1 2 3 Bellcore (December 1997). SR-2275 Bellcore Notes of the Networks. Piscataway, NJ: Bellcore. pp. 6–230.
  2. ↑ Dryburgh, Lee; Hewett, Jeff (2005). Signaling System No.7 (SS7/C7) Protocol, Architecture, and Services. Indianapolis: Cisco Press. p. 14. ISBN   1-58705-040-4.
  3. ↑ "AUSTRALIAN STANDARD AS/CA S003.1:2010 Requirements for Customer Access Equipment for connection to a Telecommunications Network" (PDF). 2010.
  4. ↑ "Telephone Ring Voltage Tech Bulletin". sandman.com. Sep 14, 2018.
  5. ↑ "Tele-Q: Operating Telephones for Stage and Screen". www.tele-q.com.
  6. ↑ "Telephone Ring Generator - Phone ringer for the stage". www.precisiovision.freeuk.com.
  7. ↑ "Telephone Ring Generator - Ringer Power Supply - Viking Industrial Product". vikingindustrialproducts.com.
  8. ↑ "Telephone Circuits Page". www.qsl.net.
  9. ↑ "Telephone Ring Generator Using Small Power Transformer". www.diyelectronicsprojects.com. Archived from the original on April 10, 2016. Retrieved 2021-05-22.
  10. ↑ "Telephone ringing circuits". www.epanorama.net.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.