ON=OFF switching circuit connected to telephone microphone - operates during conversation depending on orientation of handset

摘要

The on/off switching circuit uses a tube filled with mercury to switch off the handset microphone when the handset is held in a given position. The mercury makes or breaks contact between two contacts inside the tube. The tube is made of glass and may be rod-shaped or shaped like a hook. The tube is designed to fit into the telephone handset or into the microphone assembly (being mounted either on the outer or inner wall of the microphone capsule). The advantage lies in being able to interrupt a conversation simply by holding the handset in a given position.