01-08-2012, 04:10 PM
THE EMERGENCE OF COMMERCIAL DIGITAL SATELLITE COMMUNICATIONS
TELECOM STATE OF THE ART CIRCA 1960
The state of the art for international communications was
determined by the postal telephone and telegraph administrations
(PTTs) of the world. The national monopolies of
each country organized their networks and agreements in
the Consultive Committee for International Radio (CCIR)
and International Telegraph and Telephone Consultive
Committee (CCITT) of the International Telecommunication
Union (ITU) so that their traffic would interface seamlessly
at major switching points in their respective countries.
These switches were electro-mechanical. At the endpoints or
last mile, four-wire voice circuits were terminated in twowire
connections at user handsets. The voice bandwidth was
4 kHz/channel. Any data that was transmitted or received
was limited to this bandwidth and worked well because data
rates were very low. The data speed varied, but we are talking
about 50–120 b/s, which represented a very low percentage
of voice traffic.
COMSAT LABORATORIES
Comsat Laboratories (Fig. 1) opened in September 1969
under Wilbur Pritchard as director of research and development.
It was a wonderful place to work as an engineer, and
was wide open to improving spacecraft, antenna systems,
baseband communication systems, propulsion, and much
more.
The atmosphere was creative, and accomplishments were
made across the board. New satellite applications such as
television broadcasting, maritime, and private corporate
networks were on the horizon. Comsat Labs was a place
where all aspects of satellite communications were under
scrutiny and improvement for commercial operations. The
Intelsat program included engineers and staff from consortium
countries who stayed on for two years or so and
brought their own ideas. I was recruited to Comsat from
IBM as a digital design engineer. At IBM I was developing
a digital wireline modem at the “high speed” of 2400 b/s to
access IBM mainframe computers. Access to the corporate
mainframe computers over voice-based landlines without
the need to have an independent mainframe at each major
location was evolving. Being the only digital engineer at
Comsat in its early days left me with time to look at the use
of digital transmission for the developing network. I believe
there were only 15 employees at Comsat at the time —
November 1963.
TELECOM STATE OF THE ART CIRCA 1960
The state of the art for international communications was
determined by the postal telephone and telegraph administrations
(PTTs) of the world. The national monopolies of
each country organized their networks and agreements in
the Consultive Committee for International Radio (CCIR)
and International Telegraph and Telephone Consultive
Committee (CCITT) of the International Telecommunication
Union (ITU) so that their traffic would interface seamlessly
at major switching points in their respective countries.
These switches were electro-mechanical. At the endpoints or
last mile, four-wire voice circuits were terminated in twowire
connections at user handsets. The voice bandwidth was
4 kHz/channel. Any data that was transmitted or received
was limited to this bandwidth and worked well because data
rates were very low. The data speed varied, but we are talking
about 50–120 b/s, which represented a very low percentage
of voice traffic.
COMSAT LABORATORIES
Comsat Laboratories (Fig. 1) opened in September 1969
under Wilbur Pritchard as director of research and development.
It was a wonderful place to work as an engineer, and
was wide open to improving spacecraft, antenna systems,
baseband communication systems, propulsion, and much
more.
The atmosphere was creative, and accomplishments were
made across the board. New satellite applications such as
television broadcasting, maritime, and private corporate
networks were on the horizon. Comsat Labs was a place
where all aspects of satellite communications were under
scrutiny and improvement for commercial operations. The
Intelsat program included engineers and staff from consortium
countries who stayed on for two years or so and
brought their own ideas. I was recruited to Comsat from
IBM as a digital design engineer. At IBM I was developing
a digital wireline modem at the “high speed” of 2400 b/s to
access IBM mainframe computers. Access to the corporate
mainframe computers over voice-based landlines without
the need to have an independent mainframe at each major
location was evolving. Being the only digital engineer at
Comsat in its early days left me with time to look at the use
of digital transmission for the developing network. I believe
there were only 15 employees at Comsat at the time —
November 1963.