Pushbutton keyboard for subscribers telephone set - has sliding tubes acting as guides for internal and external helical springs of buttons

摘要

The pushbutton keyboard has a contact ring moving when a button is pressed and contacting a printed circuit board connected to the selection signal generator. A moving guide supports the button. A first spring returns the button and guide to their rest positions. A second spring coaxial with the first pushes the contact ring against a stop on the guide when in the rest position. A single stationary tube has its inside surface guiding the first spring and its outside surface guiding the second spring. The tube is concentric with the contact ring and slides longitudinally.