The exact number required has never been disclosed but one or two orders is insufficient. Sufficient complaining and pointing out that other residential exchanges nearby have ISDN capability has spurred Telecom to reconsider and implement the exchange upgrades. One reason given for this policy was the high cost and limited availability of the exchange isdn equipment. Also as recently as last quarter 1996 into January 1997 there was an extreme shortage of NT units and other hardware that needs to be installed in customer premises. This has been reported in the computer press for that period.
Telecom seem to order the equipment on a minimal basis.
A similar situation exists with Digital Data Services. This depends on your location. The installation may be more if Telecom have difficulty in getting additional copper cables into your property. It will definitely NOT cover the cost of an excavation if a new underground cable needs to be installed. If not then you will be paying for a new trunking to be installed.