Analogue Data Circuits

What are analogue data circuits?

A Telecom NZ service :-(
This is a Telecom data service which uses normal telephone type circuits to provide a data transfer capability. There is no speed restriction on these circuits as Telecom only provide a jack socket at each end of the link.
The customer must then provide the appropriate modem equipment, this must be Telecom approved modems.
There is no guarantee that such circuits will work at the full capability of any modem. Reports from people with analogue leased lines vary in the reliability, lack of line noise and the most reliable modem throughput. 19K2 bits per second appears in a lot of cases to be the maximum throughput such links can handle although factors such as distance from exchange and condition of the physical circuit is a factor in throughput.

Telecom have said that they are phasing out these type of data services in favour of their Digital Data Services.

Types of Telecom analogue circuits
There are three type of analogue leased line available:

  • An A1 circuit, a 2 wire non conditioned connection between the ends of the circuit. pair.
  • An A2 circuit, a four wire non conditioned connection.
  • An A3 circuit, a four wire circuit specially conditioned for data. This circuit is supposed to be of better quality and the most reliable analogue circuit available.

    What does it cost?

    Installation for A1 and A2 is $420 per end, A3 is $520 per end. Monthly analogue circuit charges consist of an access charge at each end then a fixed step charge between the two ends of the circuit.
    Until recently there was also a distance charge but this has not been removed. Access per end: A1 $45, A2 $90, A3 $90.
    Fixed City step charge is $90.

    So for example an A1 circuit within the free dial area of Auckland would cost $820 installation then the monthly rental would be $45+$45+$90 = $180.

    Ordering an analogue link

    These can be obtained from the nearest Telecom Business Centre or Sales office and they will post original copies to you or fax them directly.

    The application consists of four pages.
    Page 1. General Company information and billing addresses Pages 2 and 3. The site drop information, address, contact people, location in building where link is to be terminated. There is one page for each end of the link. You will have to contact your Internet Service Provider to get the exact details to complete for their end of your link. Some service providers prefer to complete the whole document as it makes sure there are no delays due to incorrect or missing answers.
    Page 4. Analogue circuit type A1, A2 or A3.

    After the completed application is returned to Telecom it can take anything from one day to 15 days for the circuit to be installed. Normal installation time is about 5 to 7 days. In any case Telecom will provide a latest date for commissioning the new link.


    Just about all analogue (telephone) installations are now carried out by Installation companies that contract to Telecom.

    An A1 analogue circuit requires a single copper line pair. A2 and A3 circuits need two copper line pairs. These data circuits cannot be installed on a line used for 1+1 or other multiplexing schemes for providing more than one analogue (phone) service over a copper pair.
    The installation cost will include stringing an overhead cable from a Telecom street pole to the building and hence to the required outlet location. It will NOT include installing new trunking or excavating for an underground cable on the customer's property or building.

    An analogue link is terminated at each end in a standard Telecom jack socket. It will be labelled as a data circuit and may have a warning not to be used with a telephone handset.

    Internet connection using analogue circuits

    Analogue circuits are a viable low cost internet connection where the distances between the ends of the circuit are less than a few kilometers. Where both ends of the circuit terminate in the same exchange then the overall cost can be little more than a normal telephone circuit. The main advantage over a business telephone line is that there is no per moinute connection charge. One flat monthly cost is all that is involved.
    The main problem with analogue circuits is that they use analogue signalling between modems at each end of the link. This is prone to interference, line noise and drop-outs. Modems have always been a problem. Just getting suitable modems for use with such circuits can be a problem. Getting a modem that can work reliably at the higher modem speeds (28k8 to 33k6) can be almost impossible.

    Modems for use with analogue data circuits A modem on an analogue circuit is normally set up to work in leased line mode. This will be a configurable feature of the modem. Modems know to work over analogue circuits include: Zyxel modems, most in their standard range have two wire leased line settings.
    Comet modems, all support two wire leased lines

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    Last modified: 5 May 1997.