Dictograph Intercom, 1943
Installed at Russell Street police headquarters in 1943, the Dictograph was used to create an intercom telephone network.
The device transmitted and magnified sound using a powerful microphone. Due to the success of the microphone technology, a version of was also developed specifically for surveillance work by police in the US and UK, referred to as the Detective Dictograph. The device was also marketed as a means to discover cheating spouses!