As you look down the room, behind you is a long telephone "primary" testboard. Primary because it is where the toll cables come in from the cable head at the distributing frame. This is the north side of the building facing an alley called Ludlow Street. Beyond that a block further north is Market Street. To your right is 5th Street; to the left the building stretches all the way to 4th St. Looking straight ahead past the duplex tables is another telephone primary board. On the far side of the wall behind this board was the test table room, which is where local cables were tested and troubles requiring the attention of an equipment attendant were referred. Still further was a terminal room where local cables from the Bell Co. terminated on the "Main Frame" or various Intermediate distributing frames-IDF. Also ring-down toll line equipments associated with LD telephone circuits. Then came another alley, Ranstead Street and a block further on, Chestnut.
This photograph shows the AT&T operation as it existed in the early 1920s. The elevated structure on the left was called the "Pulpit" from which an attendant could survey the entire room. If you look closely at the SLR shelves vertical pipe-like affairs are sticking up. These are calling-in signals which could be brought up by a customer experiencing some kind of problem. These lamps could be seen from the pulpit and some one dispatched to the repeater to see what the problem was. In the older telephone and telegraph plant, everything was sectionalized. Equipment and cables were brought to distributing frames and cross-connected through jack circuits-which were in the morseboards/testboards-in whatever configuration was needed. The jack circuits permitted access to every element of a given circuit for testing and patching. For example if a repeater or cable failed, the circuit could be restored quickly by patching the part in trouble off to a spare or "make-good". There were grounded-line boards that terminated simplexed lines - circuit units - composite line boards the composite legs for circuit units so derived , duplex boards for the repeaters, loop boards for looping customers into the mainline or backbone circuit. Telegraph stuff had lots of legs- send legs, receive legs, composite legs, simplex legs connected to lines and drops and loops.
Under the repeater tables are the bridge coil and a composite coil associated with the set's artificial line arranged so that it can be switched in or out to permit obtaining a balance, depending on the nature of the line facility in use. Condensers that make up part of the artificial line as well as the spark killers, flat 18-type current regulating resistances etc. are down there as well. The composite sets are located elsewhere, the telephone sides going to voice repeaters and the composite legs, as I said, to composite line jacks at the Morseboard.
In 1879 the (then) National Bell Telephone Co. and Western Union settled their big patent fight, with WU agreeing to stay out of the telephone business and the phone company agreeing to stay out of the PUBLIC MESSAGE telegraph business. They didn't say anything about leased wire telegraph. So, AT&T offered private leased wire service to all comers. The customers were every sort of industrial or business concern there was - brokerage houses -AP, UP, steel , the works. Just about all of the long haul circuits were four wire composited, either transposed open wire or cable, while short haul facilities were generally two wire voice with simplexes. Picture the wire coming in from the line, through the composite set to the line side of a repeater, the send leg in half duplex operation, or both send and receive legs in full duplex operation being brought out to the drop jack of a Morse line terminal jack circuit. This is where loops to the customer would be either inserted with a cord (looped in) into a looping jack or, in later practice, the loop would be directly on a loop jack. The subscribers loop was made up of local Bell company pairs strung together to reach his location. Always pairs- balanced; to work single grounded wire would noise up the telephone cable. If the subscriber was too remote he would be tied in with a differential repeater working over a simplex grounded unit to the nearest equipped office and looped in from there.
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