Zurich automatic tandem toll exchange

The progress of the Swiss telephone service over the last 20 years is described. A map shows the automatic toll network of the country in its present form. The three different classes of selective trunk services are discussed, also the two classes of incoming toll lines. Automatic toll connections can be made directly by subscribers. Two wire lines using 50 c/s signalling and 4-wire lines using 3 000 c/s signalling with automatically inserted repeaters with auto-gain control are used. A simplified junction diagram and photos of the Zurich exchange are given.