I grew up near Pennsburg, PA. When we move there in the mid 1970′s it was a small town of perhaps 1000 people, surrounded by large tracts of farm land. Up the road from us, about a 5-10 minute walk, was one of those AT&T microwave relay stations. The Long Lines system is not only a technological achievement, one which is sadly forgotten, and yet part of our daily lives from 1960-1990. It looks something like this:
These facilities were spaces about 40-50 miles in any given direction to form a network that spanned the continental United States. From 1960-1990 virtually all long distance calls were routed over this network, consisting of several thousand stations.
It consisted of three technologies. In common was AT&T’s long distance central office switching system. In addition AT&T employed two technologies to interconnect these CO’s to each other. The majority of calls ( 70% ) were routed over UHF over coaxial cables which connected the sites together. Bundles of cables formed trunks, and several trunks would be run through conduit. Much like analog cable TV, the UHF spectum was divided into channels, each capable of carrying an analog call. In areas where it was difficult or expensive to run cables, they transmitted these UHF, and later, millimeter wave signals to create a broadband, wireless, point to point connection. This accommodated the remaining 30% of the network capacity.
The underground cables hedged against transient atmospheric interference ( thunderstorms, etc. ) and the wireless links hedged against someone digging up the cables. And being a network, calls could be routed around failed CO’s with a few extra hops around. Either way, this was a broadband system which chunked up the particular transmission mediums spectrum into channels which could carry voice.
It was actually possible, with a UHF reciever, to listen in on these conversations. You would hear a few control tones, which told the next switch in line how to route the call, and then one side of the phone call. The other side if the call would be carried via a different frequency, or perhaps different trunk entirely.
Larger chunks of spectrum could carry other signals, including TV signals. In essence, Long Lines served as the countries video distribution network. It enabled the first simultaneous broadcasts. And without the delays introduced by satelite, provided for the first real time video conferences. Without Long Lines there would have been no “And now we go live to our reporter Sally Smiley Face ( 2000 miles away )…”
This communication facility was also used by the US Government and military. As the specter of thermonuclear war emerged in the 1960′s, measures were taken to harden these facilities to better protect it from this perceived threat. AT&T’s strategy was to build the network around primary and secondary targets. This explains why most of these towers were out in the middle of no where.
As a result, most of the above ground struictures were designed to handle a 2psi pressure wave, as was the tower structure. This is roughly equal to a 300 MPH wind – which is the highest observed in a tornado – by no accident. Now when you have a 50′ x 20′ wall, that translates to about 150 tons! Typically steel reinforced concrete walls, special care in attaching the walls to the foundation, and a strong roof were the design elements used.
Unfortunately the pressure wave of a direct hit from a 10 mega-ton thermonuclear war head is something like 50-100 PSI. So in the 1960′s AT&T developed a couple additional levels of hardening, including a 10PSI above ground structure, and an underground bunker criteria capable of surviving a direct hit.
I lived near the Finland station which consisted of 2 stations. The above ground station and tower, similar to that seen above, was Finland 1, and was designed to withstand a 10psi pressure wave. Later the Finland 2 bunker compex was constructed. And it eventually housed the switching systems there were to have been placed in the Finland 1 facility. Yes, they built a hardened above ground building, designed to withstand a nuclear attack, only to decide that simply wasn’t good enough!
The Finland 2 bunker complex was one of the larger of its kind. Only 2 larger bunkers were constructed. It was a single level structure, about 10,000 sf.
I was given a tour of the Finland 2 bunker ( actual plans above ) when it was still in operation in 1984. In retrospect, I consider this a real privilege, as very few people, other than the small number of AT&T technicians who manned these facilities, actually got to see them in operation. It was an amazing experience, and one I remember very vividly.
I was just 16 years old, enrolled in an electronics tech program in high school. I had to interview someone in the field and write a report. So I walked up to the facility, 5 minutes from my house, and went to the front entrance. It was a small 4′ square foyer with a security door, a cylindrical key and numeric key pad, and a phone with no dial pad. There was an ominous sign indicating that I may have already committed several federal crimes just by reading the sign.
I picked up the phone, and an operator answered. In said my piece and they said I should speak to someone named Mr. Miller ( I think? ) and that I should come back at a later date. I did. The man came out to greet me. He asked a bunch of questions, which I must have answered correctly.
He walked me into his office. and we spend about 5 minutes in the building, he explained its special design, and so on. There was nobody there. I remember there being a large open area with a few racks of equipment, but completely out of scale for the size of the stricture. Then we led me out side. I figured “well that’s it, nothing to see here.”
“Well, here is something I think you’ll find interesting.” He led me over to a small garage with a couple steel garage doors, and a similar alcove with the ominous signage, and a black phone reciever. He picked up the reciever, and had a conversation, and Bzzzzt! the conventional looking door opened up. We went in and then down a metal stairway. It seemed to gown down perhaps 20-30 feet.
We exited the stairwell into a small room, with high cielings. There was a tall hangar style door which he entered a code on a keypad, and it unlocked. Through this door was a hallway which we walked down a few feet, then we reached an locker room looking area with shower heads, lockers, and benches. passing through this area we backtracked down another hallway and reached a huge steel bank vault door. There was another key pad and phone. He said he was talking to someone in Virginia, and then you could hear a Whump! which i was told were magnetic locks disengaging. Then he opened he vault door, which I guess about about 10-12 feet tall.
By then I had forgotten all the stairs. We entered this long gallery which seemd to have 18-20′ high cielings, and a mesannine level along both sides. To the left was a set of refrigerator sized batteries. Each was a 1.5v lead acid cell. There were a large number of them. He indicated that the whole array would only powere the equipment for a couple minutes till the generators, in another area, would kick in. A network of copper re-bar carried the powere from the batteries to the racks and racks of equipment. Cable trays, syspended from the cieling, carried all the interconnections. Many of the racks had bays with a number of 6″ high cards.
The room was huge. Much larger than the footprint of the surface would indicate. The mezzanine level, which projected over the floor by about 10 feet, were living quarters and offices. He indicated that the facility was to be manned by 4-6 people. During a nuclear war, they had enough resources to keep the facility going for 2 months. They had a repair shop, including lathe, drill press, and so on. Ventilation was required to keep the facility from overheating, and was run through particulate filters to remove radioactive fallout.
The point of the facility wan not that the tower would survive, as many people seem to be confused about, but rather this protected the coaxial network – which was burred and would survive. This ensured the military and government would still have dial tone.
The facility also had blast detectors, which were perhaps 3-4′ tall, 12″ diameter tubes protruding from the ground with rounded tops. These fed into the bunker, and the relative delay between them detecting a pressure wave would indicate the direction and proximity of the blast. Oh, joy!
I woud visit the tower facility often, as I had before, as the 3o’ flat concrete wall of the facility was used by the locals to play tennis or “wall-e-ball” There were always a couple tennis balls stuck in the side of the building.
After my visit in the mid 1980′s, over the years, the number of cars in the parking lot decreased steadily. And by the 1990′s it was largely vacant. Then sold. I later found out that the facility, mike many of the Long Lines facilities, were sold very cheap. Its one of the regrets of my life ( no, I’m serious ) that I could not have purchased and preserved this important site. But after 15 years in moth balls, the Finland 2 site has been reborn again, and is used to – from what I’m told – to house an operations center for some part of the nations power grid. Perhaps if I wait long enough, I’ll have another chance at owning this facility.