Ted Both's Visitel used by GMH during WWII to transmit technical drawings between Adelaide, Melbourne
Inventor Ted Both showing his Visitel system, transmitting written information by telehone lines, to executives of Gneeral Motors Holden who used it to for technical exchanges between their Adelaide and Melbourne pants during World War II. At right: The quality of the transmitted information.
Pen recorders and the Visitel machine (1940-41), that allowed written information to be transmitted over long distances via telephone lines, were two communication tools among the prolific array of inventions by Adelaide’s Ted Both.
Working with his brother Don at their Adelaide laboratory as the Both Equipment Company, Ted Both was particularly proud of his Visitel. It worked by electrically encoding, on an x-y plane, the position of the pen as it wrote or drew he information. (Elisha Gray had received a US patent for a very similar system, the telautograph, in 1888.)
The Visitel used analog techniques generating vertical and horizontal signals that activated frequency-modulated audio frequency carriers to convey the position of the pen to the receiver. The unit was operated by a pen/pencil inserted into a small lever that allowed natural writing and drawing. The output from the device was very close to the original, allowing two-way technical discussions with text and drawings.
A set of Visitels was used by General Motors Holden between their Adelaide and Melbourne plants when they were making equipment for the defence forces during World War II. But the army directorate placed a secret designation on the device for 10 years, meaning Both couldn’t commercialise it during that period. By the time it was released, he had largely lost interest in it.
More successful commercially were pen recorders that became a core product for the Both company. Pen recorders were in big demand, with scientists needing to permanently record measurements. The pen recorder writing system, originally used in the first electrocardiograph, was developed into an ink-pen-on-paper system with a robust moving coil driver and became the standard for all recording equipment made by Both.
A wide range of pen recorders was built that operated at an impressive range of zero to 150Hz and comprised up to eight analog channels. Event recorders containing up to 32 channels were produced by Both as well. Among many other applications, these recorders were used for recording rainfall, oceanographic events and communications reliability. Units were often custom made and used as far away as Cape Canaveral (now Cape Kennedy) in the USA or Antarctica.
