Having in view this national, universal, articulating monopoly, Vail insisted on his second great principle, the standardization of equipment.

Every man's telephone must be precisely like every other man's, and that must be the best which mechanical skill and inventive genius could produce.

To make this a reality and to secure perfect supervision and upkeep, it was necessary that telephones should not be sold but leased.

By enforcing these ideas Vail saved the United States from the chaos which exists in certain other countries, such as France, where each subscriber purchases his own instrument, making his selection from about forty different varieties.

That certain dangers were inherent in this universal system Vail understood.