Prepaid telephone calls are a popular way of making telephone call

Telephone call

A telephone call is a connection over a telephone network between the calling party and the called party.-Information transmission:A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile...

s which allow the caller to control spending without making a commitment with the telephone company

Telephone company

A telephone company is a service provider of telecommunications services such as telephony and data communications access. Many were at one time nationalized or state-regulated monopolies...

.

Prepaid phone cards are provided by various telecom companies. When you purchase a prepaid phone card, you are paying for long distance connection time in advance. When you make calls using the phone card, the card's value is deducted based on connection fee, duration of connection, surcharges and any maintenance charges associated with the phone card.

Prepaid telephone calls are usually implemented in the company's network using the intelligent network

Intelligent network

The Intelligent Network , is the standard network architecture specified in the . It is intended for fixed as well as mobile telecom networks...

 functionality. The competitive prices these operators offer are usually made possible by least cost routing

Least cost routing

In voice telecommunications, least-cost routing is the process of selecting the path of outbound communications traffic based on cost. Within a telecoms carrier, an LCR team might periodically choose between routes from several or even hundreds of carriers for destinations across the world...

 and lower overheads than the larger telephone operators.

Types of prepaid calling

• Telephone prepaid calling cards
  Telephone card
  A telephone card, calling card or phone card for short, is a small plastic card, sized and shaped like a credit card, used to pay for telephone services. It is not necessary to have the physical card except with a stored-value system; knowledge of the access telephone number to dial and the PIN is...
  
  (commonly known as Phone Cards in the US and the UK) are available from newsstands and drugstores. They are often the cheapest means of making long-distance or even international telephone calls. Moreover, they offer complete anonymity
  Anonymity
  Anonymity is derived from the Greek word ἀνωνυμία, anonymia, meaning "without a name" or "namelessness". In colloquial use, anonymity typically refers to the state of an individual's personal identity, or personally identifiable information, being publicly unknown.There are many reasons why a...
  
  . Phone cards sold by retailers are live (active) when purchased by consumers.
• Web sites offer prepaid Personal identification number
  Personal identification number
  A personal identification number is a secret numeric password shared between a user and a system that can be used to authenticate the user to the system. Typically, the user is required to provide a non-confidential user identifier or token and a confidential PIN to gain access to the system...
  
  s (PINs) for calling; thus there is no physical phone card. Prepaid online calling cards are more convenient to use, because most of the companies provide the option of registering the phone and avoiding using PINs at all. Rates vary from provider to provider, but the customer should be aware that cards with cheaper rates usually have hidden maintenance and/or connection fees.
• Prepaid calling operators offer services to customers who hold accounts with them and have paid money in advance. The service is typically accessed by the user dialling a toll free number from any telephone (PSTN, call box, mobile phone
  Mobile phone
  A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
  
   etc). The user then authenticates himself with the operator by entering a PIN, types in the digits of the number to connect to, and then is connected by the operator. Often these operators have toll free numbers all over the world, so a customer can access the service even when he is abroad.
• Prepaid mobile phones are offered by most mobile phone operators around the world. Typically all the usual mobile phone services are available to prepaid users, except that they have to top up their balance in advance before they can be used. This is done via a variety of mechanisms - vouchers (commonly called "power cards"), swipe cards, debit and credit cards. An IVR
  Interactive voice response
  Interactive voice response is a technology that allows a computer to interact with humans through the use of voice and DTMF keypad inputs....
  
   is usually provided to allow the user to find out his current balance by dialling a short code. After the balance has been topped up, a user may make calls, send text messages and listen to voicemail in the usual way. For mobile prepaid typically use INAP
  INAP
  The Intelligent Network Application Part is a signalling protocol used in the intelligent network architecture. It is part of the SS7 protocol suite, typically layered on top of TCAP.It can also be termed as logic for controlling telecommunication services migrated from traditional switching...
  
   or CAP
  Camel Application Part
  The CAMEL Application Part is a signalling protocol used in the Intelligent Network architecture. CAP is a Remote Operations Service Element user protocol, and as such is layered on top of the Transaction Capabilities Application Part of the SS#7 protocol suite...
  
  protocol.