Country links
The PSTN began to connect the telephone systems of countries into a global network. Even in 1839 it was evident that to have a viable communication system, the telegraph cables would need to cross the largest oceans.
By 1850 The comparatively easy to achieve link between France and England was completed across the English Channel.
By 1857 attempts were begun on laying a transatlantic cable. And the route taken by the cable of 1858 is shown here:
The first cable with reliable performance was laid in 1866, and at the same time the earlier 1865 cable was repaired and brought into service.
The cable connection across the Atlantic ocean continued to develop in reliability and number of channels.