> A look at small town telephone directories of the 1960s showed dialing
> was both limited and cumbersome in many places. To reach a neighbor-
> ing exchange, one might have to dial a special prefix, and a different
> prefix for each area, as well as from where you're calling from. The
> charts could be rather complex.
It was the same in Britain at that time, with local routing codes
being used extensively. Small exchanges serving villages and rural
areas (referred to as dependent exchanges) dialed 9 to reach their
parent office, and callers on the latter would dial two-digit codes to
reach those outlying places, most commonly 8x, but sometimes other
combinations such as 5x, 6x, or 7x.
Calls from one dependent exchange to another within the area used the
parent exchange as a tandem, with listed codes which made the routing
perfectly obvious, e.g. dial 983 plus the local number.
Trunks between the parent exchange and its counterpart in a
neighboring area were accessed with more codes, typically 9x. These
outgoing trunks were made accessible from incoming trunks so that the
dependent exchanges could "dial through." Thus a call from a
dependent exchange in one area to a dependent exchange in an adjoining
area would result in two tandem exchanges and a listed routing code
which was quite long, e.g. 99182, in which the first 9 routes to the
parent exchange, 91 selects a trunk to the neighboring area, then 82
routes to a dependent exchange (and the chances are that after all
that the local number in that tiny office would be only three digits
Just to complicate matters further, if there was sufficient traffic
between two points direct trunks could be installed and a completely
separate direct routing code added, sometimes just a single digit on a
spare first level (e.g. "For calls to ______, dial 6 plus the
The way that the routing codes varied from one office to another meant
that dialing cards or booklets were issued separate from the phone
books instructing callers how to dial nearby places from their phone.
Of course, armed with a whole batch of such cards from the area, it
wasn't difficult to map out almost the entire system of routing codes
and figure out ways of routing calls which were not officially
sanctioned. In fact in some cases it allowed a call which should have
been charged at long-distance rates to be placed as a local call.
These local routings survived right up until the 1980s.