Source : Free On-Line Dictionary of Computing

TYMNET
     
         A United States-wide commercial computer
        network, created by {Tymshare, Inc.} some time before 1970,
        and used for {remote login} and file transfer.  The network
        public went live in November 1971.
     
        In its original implementation, it consisted of fairly simple
        circuit-oriented {nodes}, whose circuits were created by
        central network supervisors writing into the appropriate
        nodes' "permuter tables".  The supervisors also performed
        login validations as well as circuit management.  Circuits
        were character oriented and the network was oriented toward
        interactive character-by-character {full-duplex}
        communications circuits.
     
        The network had more than one supervisor running, but only one
        was active, the others being put to sleep with "sleeping pill"
        messages.  If the active supervisor went down, all the others
        would wake up and battle for control of the network.  After
        the battle, the supervisor with the highest pre-set priority
        would dominate, and the network would then again be controlled
        by only one supervisor.  (During the takeover battle, the net
        consisted of subsets of itself across which new circuits could
        not be built).  Existing circuits were not affected by
        supervisor switches.
     
        There was a clever scheme to switch the echoing function
        between the local node and the host based on whether or not a
        special character had been typed by the user.  Data transfers
        were also possible via "auxiliary circuits".
     
        The Tymshare hosts (which ran customer code) were {SDS 940},
        {DEC} {PDP-10}, and eventually {IBM 370} computers.  {Xerox}
        {XDS 940} might have been used if Xerox, who bought the design
        for the SDS 940 from Scientific Data Systems, had ever built
        any.
     
        The switches were originally {Varian Data Machines} 620i.  The
        {Interdata 8/32} was never used because the performance was
        disappointing.  The TYMNET Engine, based loosely on the
        Interdata 7/32, was developed instead to replace the Varian
        620i.  in the early 1990s, newer "Turbo" nodes based on the
        {Motorola 68000} began to replace the 7/32s.  These were later
        replaced with {SPARC}s.
     
        PDP-10s supported (and still do in 1999) cross-platform
        development and billing.
     
        {Tymshare, Inc.} originally wrote and implemented TYMNET to
        provide nationwide access for their {time-sharing} customers.
     
        La Roy Tymes booted up the public TYMNET in November of 1971
        and, as of March 2002, it had been running ever since without
        a single system crash.
     
        TYMNET was the largest commercial network in the United States
        in its heyday, with nodes in every major US city and a few
        overseas as well.  Tymshare acquired a French subsidiary,
        {SLIGOS}, and had TYMNET nodes in Paris, France.
     
        Tymshare sold the TYMNET network software to {TRW}, who
        created their own private network (which was not called
        TYMNET).  In about 1979, TYMNET Inc. was spun off from
        Tymshare, Inc. to continue administration and development of
        the network.
     
        TYMNET outlived its parent company Tymshare and was acquired
        by {MCI}.  As of May 1994 they still ran three {DEC KL-10}s
        under {TYMCOM-X}, although they planned to decommission them
        soon.
     
        The original creators of TYMNET included: Ann Hardy, Norm
        Hardy, Bill Frantz.  La Roy Tymes (who always insisted that
        his name was NOT the source of the name) wrote the first
        supervisor which ran on the 940.  Joe Rinde made many
        significant technical and marketing contributions.  La Roy
        wrote most of the code of the network proper.  Several others
        wrote code in support of development and administration.  Just
        recently (1999) La Roy, on contract, wrote a version of the
        supervisor to run on {SPARC} hardware.
     
        The name TYMNET was suggested by Vigril Swearingen in a weekly
        meeting between Tymshare technical and marketing staff in
        about 1970.
     
        {(http://cap-lore.com/ETH.html)}.
     
        [E-mail from La Roy Tymes]
     
        (2002-11-26)