The UAX5 was designed to give continual telephone service to rural communities, at low capital cost. For a UAX5 to be provided the minimum required number of subscribers is 8, and when the the first six have signed up, the area engineer would start looking for a site to put the exchange on. The first unit provided service for 25 subscribers, and after 23 have service, the next unit would be installed. At 46 subs the next unit is added along with a larger set of batteries. The last unit is added when the 69th sub joins. The cost of providing the exchange is roughly £500 for the site, construction of the building and fitting of the first unit, batteries, MDF etc. The subsequent units cost about £200 each, with the larger batteries cost about £300. This means that the cost of service to the 89 subs (the maximum that a UAX5 can accomodate) is £16. (all prices are at 1929 rate).