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The Step by Step Switch

This AT&T informational film describes in detail how step-by-step switches work, and demonstrates their real-time operation by calling a 5-digit phone number from another dial telephone.
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Genre: Documentaire

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Réalisateur:

Pays: United States

Durée: 8 minutes

Qualité: HD

Libération: 1951

The Step by Step Switch (1951) - IMDb  6