What does this techo term pairgain and RIM mean...

PairGain is a technology that 'splits' a copper telephone line so as to allow for the provision of more than one telephone service over that line. The use of pairgain technology on a line may mean you experience a very slow dial-up connection for a dial-up internet service, and it may prevent you from being able to obtain ADSL services.

There are three main types of pair gain systems:

1. Small pair gain
2. RIM (Remote Integrated Multiplexer), with or without a minimux installed
3. CMUX (Customer Multiplexer)

There are further categories of pairgain systems within these three main types.

What effect pair gain will have on your dial-up connection speeds or your access to ADSL will depend on which kind of pairgain system is present on your line.

1. Small pairgain systems

* Dial-up services: your dial-up speed may be slowed to around 28 kbps (kilo bits per second).
* ADSL services: you will not be able to access an ADSL service unless the pair gain system is removed or upgraded.

2. RIM pairgain systems

A RIM is like a mini-exchange that sits between the main telephone exchange and your premises. The RIM is connected to the exchange by fibre optic cable. Branching out from the RIM are copper lines linking your premises to the RIM. A device called a minimux may be installed on the RIM to allow for the provision of ADSL through an ADSL enabled exchange.

* Dial-up services: some RIM systems will slow your dial-up connection down to around 28 kbps while other RIM systems will provide 56 kbps connection speeds.
* ADSL services:
o There is a minimux installed on your RIM: if there is a free port available, then you should be able to access ADSL services (provided you are not too far away from the exchange).
o There is no minimux installed on your RIM: you will not be able to access an ADSL service unless the pair gain system is removed or a minimux is installed.

3. CMUX pair gain systems

The CMUX is a newer kind of pairgain system. A CMUX is a device similar to a RIM that can provide ADSL services.

* Dial-up services: your dial-up account should not be slowed down.
* ADSL services: you should be able to access ADSL services if there is a free port available (provided you are not too far away from the exchange).

Why did Telstra put in Pair Gain systems?

When installing new telephone network services in the 1980's and 1990's, Telstra put in pairgain systems on the telephone network in order to provide more than one telephone service over a single copper line. Telstra put in pairgain systems in fast growing areas where there was no existing telecommunications infrastructure, in order to quickly provide voice telephone services to new premises.

Many new housing estates are on RIMs, as may be office buildings, shopping centres and apartment complexes. Telstra may also have put in pairgain systems in residential or commercial areas in inner metropolitan suburbs where old cabling had to be upgraded. Many rural and regional areas have had their older style telephone exchanges replaced by RIMs.

What can you do if there is PairGain or RIM on your line?

Before moving into a new location, try to find out if the telephone line at your new premises is affected by pair gain.

If you unknowingly move into new premises that is on a pairgain system, you may find you have no access to ADSL services, incur greater than anticipated costs for your broadband service or experience a frustratingly slow dial-up service. This may be a problem especially for businesses heavily reliant on having a high-speed internet connection.

An easy way to confirm that there are no pair gain issues at your new location is to ask the previous tenant or owner if they have had ADSL at the premises. If this information is not available you may not be able to confirm whether or not there is pair gain on the telephone line to your new premises until after you transfer the telephone line into your name and apply for an ADSL service. This is because the test to see if you will be able to access ADSL (called a service qualification test) will only be carried out upon an application by a customer for an ADSL service.

Putting in your telephone number into an online ADSL service availability checker (provided on the websites of most ISPs, including Telstra) will not necessarily mean that you will be able to obtain an ADSL service. An online ADSL service availability check will generally indicate whether or not your line is on an ADSL enabled exchange but will not check to see if your line is on a pair gain system or if there are enough ports available if you are on a RIM with a minimux installed.

You should not purchase any new ADSL equipment or assume that you will be able to obtain ADSL services until a full service qualification test confirms that you will be able to access ADSL.
If you are getting a new telephone line installed at your new premises, make sure that your phone company is aware of the fact that you are wanting to use the line for ADSL internet services.

When you apply to an ISP for an ADSL service, a service qualification test will be carried out on your line to see if it is capable of supporting ADSL. The service qualification test will check to see how much 'noise' or interference there is on the line and whether or not the line is on a pair gain system.

If there is too much noise on your line (generally because your premises is too far away from the exchange) or if there is pair gain, then you may be told that you will be unable to get ADSL services. In addition any dial-up service may be slower.

If the service qualification test indicates your line is on a pair gain system then the next step will be to see if an alternate network path can be found that will bypass the pair gain system on your line.

Telstra can conduct a transposition check on your line to do this search. If the transposition check finds an alternate network path that bypasses the pairgain, your ISP should be able to provide you with ADSL services. If not, read on.

If Telstra upgrades the infrastructure in your area, the pairgain system may be removed or replaced with a newer pairgain system.

If you are on a RIM with a minimux installed but can't obtain ADSL, the problem may be that there are not enough ports available. This is because a RIM with a minimux installed only has a limited number of ports that will enable customers on an ADSL enabled exchange to access ADSL services. Demand for ADSL services in an area may exceed the number of ports available and once a number of residents in a particular area have been successful in securing an ADSL connection, the rest may be left without access to ADSL until additional ports are added or there are other infrastructure upgrades.

You will need to periodically submit new ADSL applications to check if an upgrade means you will be able to obtain ADSL.

There is generally very little you can do other than to wait for an upgrade to the infrastructure, even if you are a business and/or are willing to pay additional money. Installation of a new telephone line, if your premises is on a pairgain system, is unlikely to solve the problem. You may need to look at your other internet service options.

It is unlikely that the Telecommunications Industry Ombudsman (TIO) will have the jurisdiction to investigate problems with obtaining ADSL because of pairgain systems. However, if you've had a new telephone line installed for the purpose of obtaining ADSL services and you made this known to your phone company when requesting the new line installation, but you're unable to get ADSL because of pairgain on the line, then the TIO may be able to investigate the matter.

See the TIO website for information on its position on methods of installation of new lines.http://www.tio.com.au/POLICIES/Provisioning/Methods%20of%20installation%20of%20new%20lines.htm

Have you been told you can't get ADSL with Overflow but can get ADSL from Telstra?

The results of any service qualification test or transposition check, should be the same regardless of the ISP you made your ADSL application to. If you believe that that this has not been the case, contact the Australian Competition and Consumer Commission to obtain further information and to put in a complaint http://www.accc.gov.au/content/index.phtml/itemId/54217/fromItemId/3634

  • Email, SSL
  • 11 Users Found This Useful
Was this answer helpful?

Related Articles

Does my exchange have DSL and how many ports are left?

Please see the Telstra reports available online at...

What is my IP Address?

Please visit the following website  http://ip.oih.com.auThis will work for both ipv4 and ipv6

DSL Fault Form

NOTE: THERE IS A $300 charge if a technician attends and there is NO FAULT found in the carriers...

How to complete a DSL Fault Report

To report a DSL1 fault, please complete the following form and post in a new support ticket...

FTP Speed Tests

If you have customers reporting slow speeds please perform an FTP speed test from the following...