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Some PABX Calling Features

Auto Attendant

In telephony, an automated attendant (also auto attendant or AA) allows callers to be automatically transferred to an extension without the intervention of an operator (typically a receptionist).

Many AA will also offer a simple menu system (“for sales, press 1, for service, press 2, etc.) and it may also allow a caller to reach a live operator by dialing a number, for example ‘9’.

On a purely technical level it could be argued that an automated attendant is a very simple kind of IVR, however in the telecom industry the terms IVR and Auto Attendant are generally considered distinct – an Automated Attendant serves a very specific purpose (replace live operator and route calls), whereas an IVR can perform all sorts of functions (telephone banking, account inquiries, etc).

The following lists common routing steps that are components of an automated attendant:

  • Transfer to Extension;
  • Transfer to Voice Mail;
  • Play Message (i.e. “our address is …”);
  • Go To a Sub Menu;
  • Repeat Choices.

In addition, an Automated Attendant would be expected to have values for the following

  • ‘9’ Where to go when the caller dials ‘9’;
  • Timeout What to do if the caller does nothing (usually go to the same place as ‘9’);
  • Default mailbox Where to send calls if ‘9’ is not answered (or is not pointing to a live person).

Many auto attendants will have options to allow for time of day routing, as well as weekend and holiday routing. The specifics of these features will depend entirely on the particular automated attendant, but typically there would be a normal greeting and routing steps that would take place during normal business hours, and a different greeting and routing for non-business hours.

It has become common in industries that have recently entered the telecom industry to refer to an Automated Attendant as an IVR, however, the terms Automated Attendant and IVR are distinct and mean different things to traditional telecom professionals, whereas emerging telephony and VoIP professionals often use the term IVR as a “catch-all” to signify any kind of telephony attendant menu, even a basic automated attendant.

ACD – Automatic Call Distributor

In telephony, an Automatic Call Distributor (ACD) is a device or system that distributes incoming calls to a specific group of terminals that agents use. It is often part of a computer telephony integration (CTI) system.

Routing incoming calls is the task of the ACD system – ACD systems are often found in offices that handle large volumes of incoming phone calls from callers who have no need to talk to a specific person but who require assistance from any of multiple persons (e.g., customer service representatives) at the earliest opportunity.

The system consists of hardware for the terminals and switches, phone lines and software for the routing strategy, which is a rule-based set of instructions that tells the ACD how calls are handled inside the system. Typically this is an algorithm that determines the best available employee or employees to respond to a given incoming call. To help make this match, additional data are solicited and reviewed to find out why the customer is calling – sometimes the caller’s caller ID is used; more often a simple Interactive Voice Response is used to ascertain the reason for the call.

Originally, the ACD function was internal to the PABX of the company; however, the closed nature of these systems limited their flexibility, thus, a system was then designed to enable common computing devices, such as server PCs, to make routing decisions; for this, generally, the PABX would issue information about incoming calls to this external system and receive a direction of the call in response.

An additional function for these external routing applications is to enable CTI; this allows improved efficiency for call center agents by matching incoming phone calls with relevant data on their PC via screen pop.

Automatic Ring Back

Normally, when a person’s line is busy, one has to call back every few minutes to check if their line is free yet. With automatic ring back, a code can be dialed into the telephone keypad to enable ring back. Then, when their line is free, the original caller’s phone rings with a distinctive ring so that one knows it is automatic ring back and not a regular call and, when the phone is picked up, it calls the other number since the line is now free.

Call forwarding (on busy or absence)

Determines the routing of incoming calls when the extension is busy or not answered after a set number of rings – the exchange is configured with a number of an extension to divert calls and could even be different extensions for each of the cases – when a call comes into the original extension and is one of the mentioned situations, the call is diverted to the pre-defined extension number.

Call Park

Is a feature of some telephone systems that allows a person to put a call on hold at one telephone set and continue the conversation from any other telephone set.

The “call park” feature is activated by pressing a preprogrammed button (usually labeled “Call Park”) or a special code; this transfers the current telephone conversation to a “virtual” extension number and immediately puts the conversation on hold, allowing the call to be retrieved later.

At this point, the telephone system will often provide an option for the person to make an announcement through a public address system – often consisting of some of the telephone sets and/or overhead paging speakers controlled by the telephone system).

Making such announcements in such a way is referred to as paging. To access the paging system, the user must enter the paging access code or press the “page” button on the telephone, and announce the call parked extension.

An example would be at a grocery store where the bakery has a call parked – the user would say “Bakery you have a call parked on 627” and the bakery department would then dial 627 to access the call on hold.

A set time is then provided for any person to retrieve the call by dialing the extension number of the parked call on any telephone set.

If no one picks up the parked call within the set time, the telephone system may ring back the parked call; this transfers the parked call back to the person who originally parked it.

Call Pick-up

Is a feature used in a telephone system that allows one to answer someone else’s telephone call – this feature is accessed by pressing a preprogrammed button (usually labeled “Pick-Up”), or by pressing a special sequence of buttons on the telephone set.

The telephone sets may be divided into zones – under such an arrangement, using “call pick-up” will only pick up a call in the same zone; it’s called “zone call pick-up”.

“Call pick-up” can be directed and is used for picking up a call that is ringing at a specific extension number; this feature is accessed through a different sequence of buttons than normal “call pick-up” ; it’s called “direct call pick-up”.

As a telephone set can only pick up one call at one time; if there are several incoming calls at the same time, “call pick-up” will pick up the call that rang first unless the pick-up is directed.

Call Transfer

A call transfer is a telecommunications mechanism that enables a user to relocate an existing call to another telephone or attendant console by using the transfer button and dialing the required location. The transferred call is either announced or unannounced.

If the transferred call is announced, the desired extension is notified of the impending transfer – this is typically done by putting the caller on hold and dialing the desired extension; it is then notified and, if it choose to accept the call, it is transferred over to it.

On the other hand, an unannounced transfer is self-explanatory: it is transferred without notifying the desired extension of the impending call; it is simply transferred.

Call waiting

Call waiting, in telephony, is a feature on telephone networks – if a calling party places a call to a called party which is otherwise engaged, and the called party has the call waiting feature enabled, the called party is able to suspend the current telephone call and switch to the new incoming call and can then alternate between the two calls.

Conference Call

It’s also often referred to as an ATC (Audio Tele-Conference).

A conference call is a telephone call in which the calling party adds more than one called party into the call. Conference calls may be designed to allow the called party to participate during the call, or the call may be set up so that the called party merely listens into the call and cannot participate/speak.

Conference calls can be designed so that the calling party calls the other participants and adds them to the call – however, participants are usually able to call into the conference call themselves by dialing into a special telephone number.

Three-way calling is a feature sometimes also available. To three-way call, the first person one wishes to talk to is dialed and after answer then the “flash” button (also known as the recall button) is pressed and the other person’s phone number is dialed; after answer or while it is ringing, flash/recall is pressed again plus the code to connect the three people together – this option allows a caller to add a second outgoing call to an already connected call.

Customized Abbreviated dialing (Speed Dialing)

Is a function available on many telephone systems allowing the user to place a call by pressing a reduced number of keys. This function is particularly useful for phone users who dial certain numbers on a regular basis.

In most cases, the user stores these numbers in the phone’s memory for future use. The speed dial numbers are usually accessed by pressing a pre-determined key on the phone, followed by a one, two or three-digit code which the user assigns to each memory/number; however for ease of use, on many systems, a call may be placed by pressing and holding one key on the numeric keypad.

Direct Inward dialing (DID or DDI)

Direct dial-in (DDI) is a feature offered by telephone companies for use with their customers’ PABX systems, through ISDN Basic and Primary accesses.

In DDI service the telephone company provides one or more trunk lines for connection to the customer’s PABX and allocates a range of telephone numbers to this line (or group of lines) and forwards all calls to such numbers.

The DDI number is transmitted by the phone company as part of the dialed destination phone number, usually the last one, two or three digits, so that the PABX can route the call directly to the desired telephone extension within the organization without the need for an attendant. The PABX “knows” which extension corresponds to the DDI number thanks to an internal table that makes its association with the extension number.

The service allows direct inward call routing to each extension of the PABX while maintaining a limited number of subscriber lines to satisfy the average concurrent usage of the customer.

DDI service is usually combined with direct outward dialing (DOD) allowing PABX extensions direct outbound calling capability with identification of their DDI number.

Do Not Disturb

The Do Not Disturb or (DND) function on most PABX systems prevents calls from ringing on an extension for which DND is activated.

Some DND attributes include directing the call to a pre-assigned extension (like a secretary or assistant), busy signal, DND signal, or recorded message generated by the telephone switch – some switches allow the call to go through to the extension giving a visual indication, but not ringing. Some PABX systems allow the assignment of DND circumvention codes to supervisors.


Also known as “Find-me”: Determines the routing of incoming calls – the exchange is configured with a number of an extension where the person will be to receive calls – when a call is received for that person, the exchange routes it to that extension number.

Another possibility is, from the destination extension, request the forwarding of calls received by the original extension to that destination extension.

IVR – Interactive Voice Response

In telecommunications, IVR allows customers to access a company’s database via a telephone touchtone keypad or by speech recognition, after which they can service their own enquiries by following the instructions.

IVR systems can respond with pre-recorded or dynamically generated audio to further direct users on how to proceed and can be used to control almost any function where the interface can be broken down into a series of simple menu choices – in telecommunications applications, such as customer support lines, IVR systems generally scale well to handle large call volumes.

It has become common in industries that have recently entered the telecom industry to refer to an IVR as an Automated Attendant, however, the terms IVR and Automated Attendant are distinct and mean different things to traditional telecom professionals, whereas emerging telephony and VoIP professionals often use the term IVR as a catch-all to signify any kind of telephony menu, even a basic automated attendant.

Music on hold (MOH)

Music on hold (MOH) refers to the business practice of playing recorded music to fill the silence that would be heard by telephone callers who have been placed on hold – It’s especially common in situations involving customer service.

Night Service

In general, a night service is any service that operates at night, such as a night-time public transport service or a 24-hour telephone support service.

Night Service in telecommunications in particular is also a feature of PABX and business telephone systems, whereby for a set period during the day (usually those hours outside of normal office or work hours, when normal operator services are not provided), incoming calls are automatically redirected by the switchboard to particular telephones or other equipment, such as: an answering machine, a voice mail system, or the duty station of a night watchman.

Voice mail

Voice Mail (or Vmail or VMS, sometimes called message bank) is a centralized system of managing telephone messages for a group of people. The term is also used more broadly, to denote any system of conveying voice message, including the answering machine.

In its simplest form it has only the functions of an answering machine, using a standard telephone handset for the user interface, but it can use a centralized, computerized system rather than equipment at the individual telephone.

Voicemail systems can be much more sophisticated than answering machines in that they can, among other features:

  • Answer many phone calls at the same time;
  • Store incoming voice messages in personalized mailboxes associated with the user’s phone number;
  • Enable users to forward received messages to another voice mailbox;
  • Send messages to one or more other user’s voice mailboxes;
  • Add a voice introduction to a forwarded message;
  • Store voice messages for future delivery;
  • Make calls to a telephone or paging service to notify the user a message has arrived in his/her mailbox;
  • Provide message notification by SMS and/or e-mail, a special dial tone, or using Caller ID signaling;
  • Transfer callers to another phone number for personal assistance;
  • Play different message greetings to different callers.

Voicemail messages are stored on hard disk drives, media generally used by computers to store other forms of data, and are recorded in digitized natural human voice, similar to how music is stored on a CD – to retrieve messages, the user calls the system from any phone, logs on using the phone keypad to dial his/her own code (security code) and their messages can be retrieved immediately.

Many users can retrieve or store messages at the same time on the same voicemail system.

Many voicemail systems also offer an automated attendant facility that enable callers to a “main” business number to access directory service or self-route the call to various places such as a specific department, an extension number, or to an informational recording in a voice mailbox, etc.

Voicemail systems are often associated with office telephone systems or PABX and may also be associated with public telephone network services such as residential phones or cellular phones. Mobile phones generally have voicemail as a standard network feature.

The most modern implementations of voicemail support fax delivery to personal voice mailboxes and retrieval via printers (text-to-speech-to-text), are integrated into e-mail systems for shared directories and shared message storage (also called Unified Messaging) and use voice user interfaces (VUI), speech technologies and/or visual screen-based graphical user interfaces (GUI).