Transmission Of Digital Information over Telephone Circuits

An exploration is reported of the possibilities of a moderately fast data transmission system to use private line message facilities. A comparatively conventional system was desired to permit expeditious application. An auxiliary “word start” signal was necessary for the system considered. Transmission characteristics of a number of arrangements were examined. These included several exploratory AM vestigial sideband systems (using a spectrum similar to telephotography), double sideband AM systems, various telegraph and other multichannel systems. It was concluded that the 1600 bits per second usable over the AM vestigial sideband arrangement was about as fast as could be expected with the data system contemplated. This transmission is not as “rugged,” with respect to impulse noise and sudden level changes, as other slower arrangements, but it is expected to be satisfactory. It will require delay correction, and simple methods are considered for carrying this out.

Transmission Aspects of Data Transmission Service Using Private Line Voice Telephone Channels

Mertz¹,

Mitchell²

1957

An Experimental Visual Communication System

Becker¹,

Hefele²,

Wintringham³

1959

Substantial technical and economic benefits are obtainable by fitting a visual communication system to a specific application. Some of the considerations involved in such adaptation are discussed in this paper. An experimental system to demonstrate the specific adaptation to the problem of signature verification in a savings bank is described. It is shown that satisfactory images can be transmitted over a 5‐kilocycle sound program circuit in 5 seconds. This result is obtained by reducing both the area scanned by the transmitter and the resolution of the reproduction to the minimum required for this application.

Signaling Systems for Control of Telephone Switching

Breen¹,

Dahlbom²

1960

Telephone signaling is basically a matter of transferring information between machines, and between humans and machines. The techniques developed to accomplish this have evolved over the years in step with advances in the total telephone art. The history of this evolution is traced, starting from the early simple manual switchboard days to the present Direct Distance Dialing era. The effect of the increasing sophistication in automatic switching and transmission systems and their influence on signaling principles are discussed. Emphasis is given to the signaling systems used between central offices of the nationwide telephone network and the influence on such systems of the characteristics of switching systems and their information requirements, the transmission media and the compatibility problem. A review is made of the forms and characteristics of some of the interoffice signaling systems presently in use. In addition, the problem of signaling between Bell System and overseas telephone systems is reviewed with reference to differing information requirements, signaling techniques and new transmission media. Finally, some speculation is made on the future trends of telephone signaling systems.