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RE: [coldwarcomms] Re: Voltages

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  • charlie Fargis
    if that meter was at 5301 N 22nd street it did when I was there. On the Pentagon voice pair cable. All the time due to Metro construction To:
    Message 1 of 19 , Mar 2, 2011
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      if that meter was at 5301 N 22nd street it did when I was there.
      On the Pentagon voice pair cable. All the time due to Metro construction

      To: coldwarcomms@yahoogroups.com
      From: wb8foz@...
      Date: Wed, 2 Mar 2011 17:19:18 -0500
      Subject: Re: [coldwarcomms] Re: Voltages






























      The positive voltage one end, negative on the other, trick has been around

      since at least the early days of Trans-Atlantic cables. The repeaters are

      in series DC-wise, so the first one works on {say} neg 1500 to neg 1400

      volts. The second one was neg 1400 to neg 1300, etc. And the repeaters were

      designed to fail open; when they did, the entire 3000 volts appeared across

      it...and jumped a gap designed to melt shorted, restoring the cable with

      one repeater-worth less gain.



      (Obviously L-4 and T-1 repeaters are easier to access for repair than a

      Trans-Atlantic cable one.)



      I'm surprised L-3 used AC...



      You used to see N2 cylinders on every third GTE pole until they got their

      act together & started fixing the leaks. But that was POTS; I guess

      L-carrier could use that as well. At Garden City, there was a conventional

      gas meter on the dry air plant. It was to measure air used by the cable and

      thus show there's a leak; as normally it would not move.


















      [Non-text portions of this message have been removed]
    • Tad G
      Here s the Garden City meter setup: http://tad.grosvenor.org/gallery/d/46340-2/IMG_1795.jpg More at:
      Message 2 of 19 , Mar 2, 2011
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        Here's the Garden City meter setup:
        http://tad.grosvenor.org/gallery/d/46340-2/IMG_1795.jpg

        More at:
        http://tad.grosvenor.org/gallery/v/Miscellaneous/GardenCity/

        -Tad

        ----- Original Message -----
        From: "David" <wb8foz@...>
        To: coldwarcomms@yahoogroups.com
        Sent: Wednesday, March 2, 2011 5:19:18 PM
        Subject: Re: [coldwarcomms] Re: Voltages


        The positive voltage one end, negative on the other, trick has been around
        since at least the early days of Trans-Atlantic cables. The repeaters are
        in series DC-wise, so the first one works on {say} neg 1500 to neg 1400
        volts. The second one was neg 1400 to neg 1300, etc. And the repeaters were
        designed to fail open; when they did, the entire 3000 volts appeared across
        it...and jumped a gap designed to melt shorted, restoring the cable with
        one repeater-worth less gain.

        (Obviously L-4 and T-1 repeaters are easier to access for repair than a
        Trans-Atlantic cable one.)

        I'm surprised L-3 used AC...

        You used to see N2 cylinders on every third GTE pole until they got their
        act together & started fixing the leaks. But that was POTS; I guess
        L-carrier could use that as well. At Garden City, there was a conventional
        gas meter on the dry air plant. It was to measure air used by the cable and
        thus show there's a leak; as normally it would not move.





        ------------------------------------

        Yahoo! Groups Links
      • ajbtelecom
        I realize that Tom s original question dealt with coax systems, but the mention of T1 repeater powering with -130 VDC provides a good opportunity for me to go
        Message 3 of 19 , Mar 4, 2011
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          I realize that Tom's original question dealt with coax systems, but the mention of T1 repeater powering with -130 VDC provides a good opportunity for me to go on a tangent.

          On a _real_ T1 carrier trunk, -130 volts DC was placed on the 4-wire trunk across the transmit and receive pairs "in simplex," the same way a "phantom" circuit was derived. This involved feeding one side of the DC supply on each pair at the exact [electrical] midpoint of the terminating impedance of the pair. In the past, this would be a center tap on a repeat coil, but on modern equipment the termination and power feed is all done using solid-state components. For a very detailed explanation of the concept of derived ["phantom"] circuits, refer to the venerable tome "Principles of Electricity as Applied to Telephone and Telegraph Work," aka the AT&T Big Green Bible.

          Now days, when you order a T1 over copper, it is almost always delivered using HDSL. On a 4-wire HDSL circuit [HDSL4], the "phantom" technique is still used, but instead of 0 volts on one pair and -130 volts on the other, the voltages are typically something like -6 volts on one side and -190 volts on the other, yielding a net voltage of -184 VDC or thereabouts. A 2-wire HDSL circuit [HDSL2] puts the -6 and -190 right on the single pair. The use of negative voltages for both sides of the circuit is done in order to keep all the copper at negative potential in relation to earth, and by extension the atmosphere, which makes the copper more resistant to destructive corrosion.

          This brings us to "conditioning." While the primary purpose of the DC feed is to power repeaters and/or the line card at the remote end, it is also standard practice to have this voltage present even in a short-haul circuit with no repeaters. This is referred to as "sealing" or "conditioning" current, and it is done to prevent corrosion at joints. The default setting for modern line cards is to loop the sealing current all times, whether repeaters are present or not, and even if the circuit is inactive or "turned down." The common term for this is a "wet" trunk or pair, as opposed to a "dry" circuit, i.e., no sealing current.

          Thank you for bearing with me, I tend to go on tangents.

          Jim
          **************************************************
          Speaking from a secure undisclosed location.

          --- In coldwarcomms@yahoogroups.com, "John K Scoggin Jr \(W3JKS/AAT3BF\)" <aat3bf@...> wrote:
          >
          > IIRC, even T-1 circuits had + and/or - 130VDC on the pairs for repeater
          > power.
          >
        • David
          ... I was not aware of HDSL4; various craft folks have told me they still use conventional T1 for longer runs with repeaters. But I know it interferes with
          Message 4 of 19 , Mar 4, 2011
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            On 3/4/11 3:35 PM, ajbtelecom wrote:

            > On a 4-wire HDSL circuit [HDSL4], the "phantom" technique is still used,
            > but instead of 0 volts on one pair and -130 volts on the other, the
            > voltages are typically something like -6 volts on one side and -190
            > volts on the other, yielding a net voltage of -184 VDC or thereabouts. A
            > 2-wire HDSL circuit [HDSL2] puts the -6 and -190 right on the single
            > pair. The use of negative voltages for both sides of the circuit is done
            > in order to keep all the copper at negative potential in relation to
            > earth, and by extension the atmosphere, which makes the copper more
            > resistant to destructive corrosion.

            I was not aware of HDSL4; various craft folks have told me they still use
            conventional "T1" for longer runs with repeaters. But I know it interferes
            with ADSL. Can you chain HDSL4 repeaters now?

            Interesting on the -6v as I've never seen this. I have ..encountered... the
            -130 (or so..) more than once.

            Note the Transatlantic cables used positive on one end to double the
            voltage drop available, hence the number of repeaters. An excellent book on
            their history was written by no less then Arthur C. Clarke: How the World
            Was One: Turbulent History of Global Communications.

            Sealing current is one of those things that many know exist and few
            understand. Years ago, I had an email exchange with a Bell Labs engineer
            who was the expert on it. It has to do with burning away microscopic
            whiskers that grow at the joints. More than that I don't recall, but it did
            not take much current to make major differences.
          • v6fiero@yahoo.com
            Right before I retired as a HiCap tech 2 years ago we were using double doublers on HDSL4 that extended the loop to about 15kFt on 22ga copper. Sent via
            Message 5 of 19 , Mar 4, 2011
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              Right before I retired as a HiCap tech 2 years ago we were using "double doublers" on HDSL4 that extended the loop to about 15kFt on 22ga copper.
              Sent via BlackBerry by AT&T

              -----Original Message-----
              From: David <wb8foz@...>
              Sender: coldwarcomms@yahoogroups.com
              Date: Fri, 04 Mar 2011 16:46:22
              To: <coldwarcomms@yahoogroups.com>
              Reply-To: coldwarcomms@yahoogroups.com
              Subject: Re: [coldwarcomms] Re: Voltages

              On 3/4/11 3:35 PM, ajbtelecom wrote:

              > On a 4-wire HDSL circuit [HDSL4], the "phantom" technique is still used,
              > but instead of 0 volts on one pair and -130 volts on the other, the
              > voltages are typically something like -6 volts on one side and -190
              > volts on the other, yielding a net voltage of -184 VDC or thereabouts. A
              > 2-wire HDSL circuit [HDSL2] puts the -6 and -190 right on the single
              > pair. The use of negative voltages for both sides of the circuit is done
              > in order to keep all the copper at negative potential in relation to
              > earth, and by extension the atmosphere, which makes the copper more
              > resistant to destructive corrosion.

              I was not aware of HDSL4; various craft folks have told me they still use
              conventional "T1" for longer runs with repeaters. But I know it interferes
              with ADSL. Can you chain HDSL4 repeaters now?

              Interesting on the -6v as I've never seen this. I have ..encountered... the
              -130 (or so..) more than once.

              Note the Transatlantic cables used positive on one end to double the
              voltage drop available, hence the number of repeaters. An excellent book on
              their history was written by no less then Arthur C. Clarke: How the World
              Was One: Turbulent History of Global Communications.

              Sealing current is one of those things that many know exist and few
              understand. Years ago, I had an email exchange with a Bell Labs engineer
              who was the expert on it. It has to do with burning away microscopic
              whiskers that grow at the joints. More than that I don't recall, but it did
              not take much current to make major differences.









              [Non-text portions of this message have been removed]
            • David
              ... Interesting. But one of T1 s strengths is you can string repeaters. It seems to me that the jitter limit is 150 miles; at 6kft per repeater, that s a lot
              Message 6 of 19 , Mar 4, 2011
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                On 3/4/11 5:01 PM, v6fiero@... wrote:

                > Right before I retired as a HiCap tech 2 years ago we were using "double
                > doublers" on HDSL4 that extended the loop to about 15kFt on 22ga
                > copper.


                Interesting. But one of T1's strengths is you can string repeaters. It
                seems to me that the jitter limit is 150 miles; at 6kft per repeater,
                that's a lot of roadside cans.
              • John K Scoggin Jr (W3JKS/AAT3BF)
                Back in the day , one of the issues you could have with repeatered T-1 circuits was oscillation when the data had marginal one s density. I recall spending
                Message 7 of 19 , Mar 4, 2011
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                  "Back in the day", one of the issues you could have with repeatered T-1
                  circuits was oscillation when the data had marginal one's density.



                  I recall spending two days (I was the customer, worked for the local power
                  company) watching the local Bell guys pumping manholes and replacing cans
                  until we found the offending unit. Lots of fun! Swap till ya drop. (Which
                  is why the 3 in 24 pattern was added to bit error rate test sets. We
                  couldn't find the problem using pseudo-random. Fortunately I had a "new"
                  pair of test sets with programmable patterns.)



                  Ahh, the fun we had! It was fun to be an early adopter. :-)



                  john



                  _____________________________________



                  John K Scoggin, Jr. W3JKS/AAT3BF/AAM3EDE/AAM3RE/AAA9SL
                  US Army Military Auxiliary Radio System
                  Delaware Gateway Station AAB3DE
                  Special Consultant - Technology

                  Emergency Operations Officer - DE and Region 3
                  "Old RADEF Officers never die, they simply decay exponentially."


                  Chief Engineer
                  Mobile Communications Unit 37 (AAT3CAD/W3MCU)

                  http://www.armymars.net/ArmyMARS/MCU <http://www.armymars.net/>


                  ARRL Assistant Section Manager - Delaware

                  Member, AMSAT and Radio Society of Great Britain
                  Email: aat3bf@...
                  Telephone: (302) 451-5000



                  "There is a very fine line between a hobby and mental illness ..." - Dave
                  Barry



                  _____

                  From: coldwarcomms@yahoogroups.com [mailto:coldwarcomms@yahoogroups.com] On
                  Behalf Of David
                  Sent: Friday, March 04, 2011 5:40 PM
                  To: coldwarcomms@yahoogroups.com
                  Subject: Re: [coldwarcomms] Re: Voltages





                  On 3/4/11 5:01 PM, v6fiero@... <mailto:v6fiero%40yahoo.com> wrote:

                  > Right before I retired as a HiCap tech 2 years ago we were using "double
                  > doublers" on HDSL4 that extended the loop to about 15kFt on 22ga
                  > copper.

                  Interesting. But one of T1's strengths is you can string repeaters. It
                  seems to me that the jitter limit is 150 miles; at 6kft per repeater,
                  that's a lot of roadside cans.





                  [Non-text portions of this message have been removed]
                • David
                  ... I read up on the history of it; it goes back to 1962, yes JFK era. And the original repeaters had to use those new things called transistors. They had to
                  Message 8 of 19 , Mar 4, 2011
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                    On 3/4/11 5:47 PM, John K Scoggin Jr (W3JKS/AAT3BF) wrote:

                    > "Back in the day", one of the issues you could have with repeatered T-1
                    > circuits was oscillation when the data had marginal one's density.

                    I read up on the history of it; it goes back to 1962, yes JFK era. And the
                    original repeaters had to use those new things called transistors. They had
                    to work over the usual -40F to 120 or whatever, and with little power and
                    space, etc.

                    And that tendency to oscillate was a major problem because one singing
                    repeater would wipe out adjacent T1's. Ooops....

                    That was why there's the bit density mandate; to avoid oscillations. And
                    that's why there were closed circuit loopback jacks and now SmartJacks that
                    fall back to making traffic. I suspect current repeaters are far more
                    stable; we've learned a lot in the intervening years.
                  • widebandit
                    Ah... And hot HDSL dead wood is such a wonderful thing to come into contact with when reaching for jumpers on the vertical side of the MDF...
                    Message 9 of 19 , Mar 4, 2011
                    • 0 Attachment
                      Ah... And 'hot' HDSL dead wood is such a wonderful thing to come into contact with when reaching for jumpers on the vertical side of the MDF...

                      >
                      > I realize that Tom's original question dealt with coax systems, but the mention of T1 repeater powering with -130 VDC provides a good opportunity for me to go on a tangent.
                      >
                      > On a _real_ T1 carrier trunk, -130 volts DC was placed on the 4-wire trunk across the transmit and receive pairs "in simplex," the same way a "phantom" circuit was derived. This involved feeding one side of the DC supply on each pair at the exact [electrical] midpoint of the terminating impedance of the pair. In the past, this would be a center tap on a repeat coil, but on modern equipment the termination and power feed is all done using solid-state components. For a very detailed explanation of the concept of derived ["phantom"] circuits, refer to the venerable tome "Principles of Electricity as Applied to Telephone and Telegraph Work," aka the AT&T Big Green Bible.
                      >
                      > Now days, when you order a T1 over copper, it is almost always delivered using HDSL. On a 4-wire HDSL circuit [HDSL4], the "phantom" technique is still used, but instead of 0 volts on one pair and -130 volts on the other, the voltages are typically something like -6 volts on one side and -190 volts on the other, yielding a net voltage of -184 VDC or thereabouts. A 2-wire HDSL circuit [HDSL2] puts the -6 and -190 right on the single pair. The use of negative voltages for both sides of the circuit is done in order to keep all the copper at negative potential in relation to earth, and by extension the atmosphere, which makes the copper more resistant to destructive corrosion.
                      >
                      > This brings us to "conditioning." While the primary purpose of the DC feed is to power repeaters and/or the line card at the remote end, it is also standard practice to have this voltage present even in a short-haul circuit with no repeaters. This is referred to as "sealing" or "conditioning" current, and it is done to prevent corrosion at joints. The default setting for modern line cards is to loop the sealing current all times, whether repeaters are present or not, and even if the circuit is inactive or "turned down." The common term for this is a "wet" trunk or pair, as opposed to a "dry" circuit, i.e., no sealing current.
                      >
                      > Thank you for bearing with me, I tend to go on tangents.
                      >
                      > Jim
                      > **************************************************
                      > Speaking from a secure undisclosed location.
                      >
                      > --- In coldwarcomms@yahoogroups.com, "John K Scoggin Jr \(W3JKS/AAT3BF\)" <aat3bf@> wrote:
                      > >
                      > > IIRC, even T-1 circuits had + and/or - 130VDC on the pairs for repeater
                      > > power.
                      > >
                      >
                    • Mike O'Dell
                      I suspect you were running AMI signaling. B8ZS makes the ones density problem less severe a constraint. this matters a *lot* when you are running synchronous
                      Message 10 of 19 , Mar 4, 2011
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                        I suspect you were running AMI signaling. B8ZS makes the ones density
                        problem
                        less severe a constraint. this matters a *lot* when you are running
                        synchronous
                        data over a T1 instead of channel bank frames. without B8ZS, a
                        particular bit
                        pattern in a packet can interfere pathologically with the line coding,
                        blowing synchronization out of the water.

                        this problem also happens on optical SONET links using POS -
                        Packet-over-SONET
                        coding. the original spec for POS didn't include a scrambler before the data
                        was put into the SONET frames. The "right" bit pattern in a packet would
                        likewise destroy frame synchronization, causing much tearing of hair and
                        gnashing
                        of teeth. the solution was to put a payload bit stream through a
                        scrambler so that
                        it was essentially impossible to create the degeneracy. I chaired the
                        meeting
                        at the Memphis IETF where the boffins from Lucent and Alcatel and
                        Siemens and
                        Fujitsu were all arguing over which polynomial was adequate to guarantee
                        immunity.
                        turns out the Lucent had already implemented something in their kit so
                        they were
                        *very* insistent that theirs be adopted. it was a long afternoon. sigh.

                        -mo


                        On 3/4/11 5:47 PM, John K Scoggin Jr (W3JKS/AAT3BF) wrote:
                        > "Back in the day", one of the issues you could have with repeatered T-1
                        > circuits was oscillation when the data had marginal one's density.
                        >
                        >
                        >
                        > I recall spending two days (I was the customer, worked for the local power
                        > company) watching the local Bell guys pumping manholes and replacing cans
                        > until we found the offending unit. Lots of fun! Swap till ya drop. (Which
                        > is why the 3 in 24 pattern was added to bit error rate test sets. We
                        > couldn't find the problem using pseudo-random. Fortunately I had a "new"
                        > pair of test sets with programmable patterns.)
                        >
                        >
                        >
                        > Ahh, the fun we had! It was fun to be an early adopter. :-)
                        >
                        >
                        >
                        > john
                        >
                        >
                        >
                        > _____________________________________
                        >
                        >
                        >
                        > John K Scoggin, Jr. W3JKS/AAT3BF/AAM3EDE/AAM3RE/AAA9SL
                        > US Army Military Auxiliary Radio System
                        > Delaware Gateway Station AAB3DE
                        > Special Consultant - Technology
                        >
                        > Emergency Operations Officer - DE and Region 3
                        > "Old RADEF Officers never die, they simply decay exponentially."
                        >
                        >
                        > Chief Engineer
                        > Mobile Communications Unit 37 (AAT3CAD/W3MCU)
                        >
                        > http://www.armymars.net/ArmyMARS/MCU<http://www.armymars.net/>
                        >
                        >
                        > ARRL Assistant Section Manager - Delaware
                        >
                        > Member, AMSAT and Radio Society of Great Britain
                        > Email: aat3bf@...
                        > Telephone: (302) 451-5000
                        >
                        >
                        >
                        > "There is a very fine line between a hobby and mental illness ..." - Dave
                        > Barry
                        >
                        >
                        >
                        > _____
                        >
                        > From: coldwarcomms@yahoogroups.com [mailto:coldwarcomms@yahoogroups.com] On
                        > Behalf Of David
                        > Sent: Friday, March 04, 2011 5:40 PM
                        > To: coldwarcomms@yahoogroups.com
                        > Subject: Re: [coldwarcomms] Re: Voltages
                        >
                        >
                        >
                        >
                        >
                        > On 3/4/11 5:01 PM, v6fiero@...<mailto:v6fiero%40yahoo.com> wrote:
                        >
                        >> Right before I retired as a HiCap tech 2 years ago we were using "double
                        >> doublers" on HDSL4 that extended the loop to about 15kFt on 22ga
                        >> copper.
                        > Interesting. But one of T1's strengths is you can string repeaters. It
                        > seems to me that the jitter limit is 150 miles; at 6kft per repeater,
                        > that's a lot of roadside cans.
                        >
                        >
                        >
                        >
                        >
                        > [Non-text portions of this message have been removed]
                        >
                        >
                        >
                        > ------------------------------------
                        >
                        > Yahoo! Groups Links
                        >
                        >
                        >
                      • Joe
                        Years ago, I remember Quasi , or Quasi Random Signal Source that we would put on all the spare T1 s at the toll office to keep them from oscillating and
                        Message 11 of 19 , Mar 5, 2011
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                          Years ago, I remember "Quasi", or Quasi Random Signal Source that we
                          would put on all the spare T1's at the toll office to keep them from
                          oscillating and running wild.

                          Joe
                          > And that tendency to oscillate was a major problem because one singing
                          > repeater would wipe out adjacent T1's. Ooops....
                          >
                          > That was why there's the bit density mandate; to avoid oscillations. And
                          > that's why there were closed circuit loopback jacks and now SmartJacks that
                          > fall back to making traffic. I suspect current repeaters are far more
                          > stable; we've learned a lot in the intervening years.
                        • charlie Fargis
                          i remember that meter. It was on the L1 cable to Wash 1 and the paired cable to the Pentagon might even have been on the C&P local video cable that went to
                          Message 12 of 19 , Mar 6, 2011
                          • 0 Attachment
                            i remember that meter. It was on the L1 cable to Wash 1 and the paired cable to the Pentagon
                            might even have been on the C&P local video cable that went to Hagerstown via microwave not AT&Ts

                            That "battery room" is actually where we had 2 diesel generators. The outline of the air in and exhaust are still visible.
                            With exception of the starting 24V batteries for the diesel in that room, at the 12 volt filament string in the radio area
                            all the batteries were in the basement.
                            To: coldwarcomms@yahoogroups.com
                            From: tad@...
                            Date: Wed, 2 Mar 2011 21:45:03 -0500
                            Subject: Re: [coldwarcomms] Re: Voltages




























                            Here's the Garden City meter setup:

                            http://tad.grosvenor.org/gallery/d/46340-2/IMG_1795.jpg



                            More at:

                            http://tad.grosvenor.org/gallery/v/Miscellaneous/GardenCity/



                            -Tad



                            ----- Original Message -----

                            From: "David" <wb8foz@...>

                            To: coldwarcomms@yahoogroups.com

                            Sent: Wednesday, March 2, 2011 5:19:18 PM

                            Subject: Re: [coldwarcomms] Re: Voltages



                            The positive voltage one end, negative on the other, trick has been around

                            since at least the early days of Trans-Atlantic cables. The repeaters are

                            in series DC-wise, so the first one works on {say} neg 1500 to neg 1400

                            volts. The second one was neg 1400 to neg 1300, etc. And the repeaters were

                            designed to fail open; when they did, the entire 3000 volts appeared across

                            it...and jumped a gap designed to melt shorted, restoring the cable with

                            one repeater-worth less gain.



                            (Obviously L-4 and T-1 repeaters are easier to access for repair than a

                            Trans-Atlantic cable one.)



                            I'm surprised L-3 used AC...



                            You used to see N2 cylinders on every third GTE pole until they got their

                            act together & started fixing the leaks. But that was POTS; I guess

                            L-carrier could use that as well. At Garden City, there was a conventional

                            gas meter on the dry air plant. It was to measure air used by the cable and

                            thus show there's a leak; as normally it would not move.



                            ------------------------------------



                            Yahoo! Groups Links


















                            [Non-text portions of this message have been removed]
                          • fdg135crm
                            There an abandoned outside cable pressurizer next to a manhole on the Finksburg/Dranesville route. It can be seen here: 39.240576,-77.234211 Google street
                            Message 13 of 19 , Mar 18, 2012
                            • 0 Attachment
                              There an abandoned outside cable pressurizer next to a manhole on the Finksburg/Dranesville route. It can be seen here:

                              39.240576,-77.234211

                              Google street view shows it in slightly better condition than it is now. I have posted photos of it in the "L Cable Pressurizer" album.

                              Farrel Becker


                              --- In coldwarcomms@yahoogroups.com, charlie Fargis <lackey91@...> wrote:
                              >
                              >
                              >
                              > i remember that meter. It was on the L1 cable to Wash 1 and the paired cable to the Pentagon
                              > might even have been on the C&P local video cable that went to Hagerstown via microwave not AT&Ts
                              >
                              > That "battery room" is actually where we had 2 diesel generators. The outline of the air in and exhaust are still visible.
                              > With exception of the starting 24V batteries for the diesel in that room, at the 12 volt filament string in the radio area
                              > all the batteries were in the basement.
                              > To: coldwarcomms@yahoogroups.com
                              > From: tad@...
                              > Date: Wed, 2 Mar 2011 21:45:03 -0500
                              > Subject: Re: [coldwarcomms] Re: Voltages
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              >
                              > Here's the Garden City meter setup:
                              >
                              > http://tad.grosvenor.org/gallery/d/46340-2/IMG_1795.jpg
                              >
                              >
                              >
                              > More at:
                              >
                              > http://tad.grosvenor.org/gallery/v/Miscellaneous/GardenCity/
                              >
                              >
                              >
                              > -Tad
                              >
                              >
                              >
                              > ----- Original Message -----
                              >
                              > From: "David" <wb8foz@...>
                              >
                              > To: coldwarcomms@yahoogroups.com
                              >
                              > Sent: Wednesday, March 2, 2011 5:19:18 PM
                              >
                              > Subject: Re: [coldwarcomms] Re: Voltages
                              >
                              >
                              >
                              > The positive voltage one end, negative on the other, trick has been around
                              >
                              > since at least the early days of Trans-Atlantic cables. The repeaters are
                              >
                              > in series DC-wise, so the first one works on {say} neg 1500 to neg 1400
                              >
                              > volts. The second one was neg 1400 to neg 1300, etc. And the repeaters were
                              >
                              > designed to fail open; when they did, the entire 3000 volts appeared across
                              >
                              > it...and jumped a gap designed to melt shorted, restoring the cable with
                              >
                              > one repeater-worth less gain.
                              >
                              >
                              >
                              > (Obviously L-4 and T-1 repeaters are easier to access for repair than a
                              >
                              > Trans-Atlantic cable one.)
                              >
                              >
                              >
                              > I'm surprised L-3 used AC...
                              >
                              >
                              >
                              > You used to see N2 cylinders on every third GTE pole until they got their
                              >
                              > act together & started fixing the leaks. But that was POTS; I guess
                              >
                              > L-carrier could use that as well. At Garden City, there was a conventional
                              >
                              > gas meter on the dry air plant. It was to measure air used by the cable and
                              >
                              > thus show there's a leak; as normally it would not move.
                              >
                              >
                              >
                              > ------------------------------------
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                              >
                              > Yahoo! Groups Links
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                              > [Non-text portions of this message have been removed]
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