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Re: HAW-1 (was: Colorado L-CXR data)

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  • Dennis Sandow
    ... TASI = Time Assignment Speech Interpolation. A room-sized (in the electron tube era) machine that doubled the voice channel capacity of a submarine cable.
    Message 1 of 15 , Oct 11, 2003
      --- In coldwarcomms@yahoogroups.com, long-lines@a... wrote:
      > What's a TASI?
      >
      TASI = Time Assignment Speech Interpolation.

      A room-sized (in the electron tube era) machine that doubled the voice
      channel capacity of a submarine cable. It exploited the fact that any
      2-way voice message circuit is generally idle in one direction (say
      eastbound) while the other end is talking (say westbound).

      TASI in the TAT-1/2, HAW-1 era took about 72 operator/machine trunks
      and condensed them 2 to 1 to fill 36 physical channels in the cable.
      The TASI at each transmitting end monitored each "derived" circuit for
      talking or silence. When the circuit started talking, the TASI
      assigned it to a cable channel. It sent commands over a data-link
      channel that told the distant TASI to, for example, "Look at cable
      channel 16 and connect the output to switching machine ("derived")
      circuit number 56." The far end was simultaneously monitoring its
      transmit side of all the derived circuits and sending similar commands
      on the data link.

      Private lines and Record Carrier (RCA/WUI/ITT) telegraph bearer
      circuits were not connected through the TASIs. Adding a private line
      took away one voice channel and had the effect of removing 2 "derived"
      voice circuits from the TASI/cable.

      This worked well in that era, since the traffic was all conversational
      voice, not data - which requires a connection 100% of the time.

      TASIs were installed on the SB (48 channel) and SD (140+/- channel
      cables). By the time of the SF cables (early 70s), this channel
      multiplication scheme was no longer necessary.

      Dennis
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