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AT&T microwave course - Unit 5

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  • albertjlafrance@cs.com
    Continuing the summary of the AT&T Long Lines self-instructional course Microwave Radio - Overall Systems (OJT-60), from 1971: Unit 5 - TD Automatic
    Message 1 of 4 , Jun 1, 2001
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      Continuing the summary of the AT&T Long Lines self-instructional course
      "Microwave Radio - Overall Systems" (OJT-60), from 1971:

      Unit 5 - TD Automatic Switching

      Covers 100A and TDAS switching equipment. Both operate in a very similar
      manner.

      With a 12-channel TD system, 10 channels are assigned to either message or
      television, and two channels are for protection.

      TD systems are divided into switching sections so that only the failed
      portion of the route will switch to protection. A switching section usually
      consists of approx. 6-7 auxiliary stations covering a distance of approx. 200
      mi.

      The TDAS is the earlier system. It uses tubes, and has relays to perform the
      switching. It switches one protection channel for any of five working
      channels, so two TDAS units are needed for a full 12-channel TD system. It
      uses the regular numerical channel designations. Channels are divided into
      two groups: 1 through 6, and 7 through 12. Channels 1, 6, 7 or 12 can be
      protection channels.

      The 100A is solid-state, and switches either of two protection channels for
      any of the 10 working channels. The working channels are designated A
      through J, and the protection channels are X and Y.

      Switching is done at IF: between the FM transmitter output and the TD
      transmitter input on the transmit end of the link, and between the TD
      receiver output and the FM receiver input on the receive end.

      The Transmit and Receive protection switch controls in a section are linked
      by VF lines, transmitting in the opposite direction from the microwave link.
      There's a separate VF line for each protection channel. The receive side of
      the switching section controls the section. Control tones to perform the
      switching functions are transmitted over the VF lines. Both TDAS and 100A
      can be operated manually.

      For either manual or automatic operation, the switch control on the receive
      end sends control tones over the VF line to the switch control on the
      transmit end. This causes the transmit IF switch to "bridge"; that is, to
      feed the IF signal into both the the working channel and the protection
      channel. Once this has occurred, the IF switch on the receive end
      disconnects the FM receiver from the working channel and connects it to the
      protection channel.
    • ozob99@yahoo.com
      ... course ... similar ... message or ... failed ... usually ... approx. 200 ... perform the ... working ... system. It ... divided into ... can be ...
      Message 2 of 4 , Jun 1, 2001
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        --- In coldwarcomms@y..., albertjlafrance@c... wrote:
        > Continuing the summary of the AT&T Long Lines self-instructional
        course
        > "Microwave Radio - Overall Systems" (OJT-60), from 1971:
        >
        > Unit 5 - TD Automatic Switching
        >
        > Covers 100A and TDAS switching equipment. Both operate in a very
        similar
        > manner.
        >
        > With a 12-channel TD system, 10 channels are assigned to either
        message or
        > television, and two channels are for protection.
        >
        > TD systems are divided into switching sections so that only the
        failed
        > portion of the route will switch to protection. A switching section
        usually
        > consists of approx. 6-7 auxiliary stations covering a distance of
        approx. 200
        > mi.
        >
        > The TDAS is the earlier system. It uses tubes, and has relays to
        perform the
        > switching. It switches one protection channel for any of five
        working
        > channels, so two TDAS units are needed for a full 12-channel TD
        system. It
        > uses the regular numerical channel designations. Channels are
        divided into
        > two groups: 1 through 6, and 7 through 12. Channels 1, 6, 7 or 12
        can be
        > protection channels.
        >
        > The 100A is solid-state, and switches either of two protection
        channels for
        > any of the 10 working channels. The working channels are designated
        A
        > through J, and the protection channels are X and Y.
        >
        > Switching is done at IF: between the FM transmitter output and the
        TD
        > transmitter input on the transmit end of the link, and between the
        TD
        > receiver output and the FM receiver input on the receive end.
        >
        > The Transmit and Receive protection switch controls in a section are
        linked
        > by VF lines, transmitting in the opposite direction from the
        microwave link.
        > There's a separate VF line for each protection channel. The receive
        side of
        > the switching section controls the section. Control tones to
        perform the
        > switching functions are transmitted over the VF lines. Both TDAS
        and 100A
        > can be operated manually.
        >
        > For either manual or automatic operation, the switch control on the
        receive
        > end sends control tones over the VF line to the switch control on
        the
        > transmit end. This causes the transmit IF switch to "bridge"; that
        is, to
        > feed the IF signal into both the the working channel and the
        protection
        > channel. Once this has occurred, the IF switch on the receive end
        > disconnects the FM receiver from the working channel and connects it
        to the
        > protection channel.


        There was a "simplified" TDAS version for single channel shots, 1
        working & 1 protection.
      • albertjlafrance@cs.com
        Were those single channel shots used for functions like sidelegs to small toll centers and for local trunks? Also, I was wondering if TDAS had automatic
        Message 3 of 4 , Jun 3, 2001
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          Were those single channel shots used for functions like sidelegs to small
          toll centers and for local trunks?

          Also, I was wondering if TDAS had automatic supervision (pilot tones or
          something like that) to monitor continuity of the VF control lines.

          Albert

          In a message dated 6/1/2001 10:17:07 PM Eastern Daylight Time,
          ozob99@... writes:

          > There was a "simplified" TDAS version for single channel shots, 1
          > working & 1 protection.
          >
        • ozob99@yahoo.com
          ... small ... or ... Yes....sidelegs like a tv channel or single MUR(message unit radio) to a small office, or to a large military customer site; e.g.
          Message 4 of 4 , Jun 3, 2001
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            --- In coldwarcomms@y..., albertjlafrance@c... wrote:
            > Were those single channel shots used for functions like sidelegs to
            small
            > toll centers and for local trunks?
            >
            > Also, I was wondering if TDAS had automatic supervision (pilot tones
            or
            > something like that) to monitor continuity of the VF control lines.
            >
            > Albert


            Yes....sidelegs like a tv channel or single MUR(message unit radio) to
            a small office, or to a large military customer site; e.g.
            Richmond-Petersburg, and Mt. Pleasant,Va(east of Richmond) TD2 Main
            station to Petersburg 50,Va Sage Direction Center at Ft Lee.

            I recall the loss of tones on the TDAS did give an alarm in either
            direction for an open in the VF path.

            Manual switching & control functions were sequential(resonant vf
            reeds)signals(much like the "sel call" used by mobile radio & airline
            communications) from the C1 Alarm Center over the ROC(Radio Order
            Circuit)transmit path.The return VF line for alarms & status was
            seperate from the ROC.



            >
            > In a message dated 6/1/2001 10:17:07 PM Eastern Daylight Time,
            > ozob99@y... writes:
            >
            > > There was a "simplified" TDAS version for single channel shots, 1
            > > working & 1 protection.
            > >
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