Electrical Communication Before Federation (continued)

Considerable innovative work was necessarily involved in extending working exchanges, providing special operator positions to handle junction traffic and developing methods of increasing traffic handling while improving service by reducing the time taken to connect calls. As maintenance of equipment, which was introduced without today's careful prototype evaluation, presented many problems to management and staff, engineering workshops were established in the various colonies to provide technical support to both the telegraph and telephone services. The Sydney network, with a relatively large number of small exchanges, developed in a rather different manner from that in Melbourne and indeed from that in comparable sized cities elsewhere. Perhaps the managers and engineers in Sydney, faced with a shortage of capital, looked to relatively low cost small exchanges which could be installed in spare corners of Post Offices. Line plant costs would also have been less, but on the other hand, operating costs of staffing numerous small exchanges and in switching larger volumes of junction traffic must have been high.

At Federation three types of exchanges, all magneto and all imported, were in use in Australia. The ubiquitous non-multiple exchange had established itself as ideal for small installations, having the advantage of low cost, ease of installation and ruggedness and, equally important in a gas lit era, its modest power needs could be met from primary cells. Transfers were needed in exchanges with three or more positions and they were usually jack ended ring down circuits and as the number of transfer groups and the proportion of transferred calls increased rapidly as the exchange grew, it was considered good practice to limit such exchanges to five positions and, because calling rates were high, a maximum of 100 lines were connected to a position.

The series multiple magneto exchange, invented in 1882, was the first satisfactory type for large exchanges, but such was the rate of progress, that by 1901 it was regarded as obsolescent, chiefly because the large number of series contacts involved were a source of faults and the exchanges were difficult to extend. Series multiple was superseded for new large exchanges by branching multiple, with self-restoring indicators and other refinements, developed overseas about 1895 and available with multiple capacities of up to 9,000 lines. Power requirements were greater and if mains power was not available, a gas engine generator using town gas was usually fitted. A fourth type, Common Battery (CB) multiple, then only recently developed, was not yet in use in Australia. It offered operating economies, better call supervision, faster service and the elimination of the generator and battery from the telephone, but was even more expensive than branching multiple and required a higher standard of line plant than did magneto. In particular, it did not tolerate earth return lines.

Australian Academy of Technological Sciences and Engineering