Connection Of Phone Wires

This is fairly easy: Just run a pair of wires from one phone to the other. One to carry the electrons out, and the other for the electrons to return--you have to have both to have a working circuit! This is just what Alexander Graham Bell did; he had one phone in his office and the other in Watson's workshop. They could talk back and forth, with no one interrupting. No batteries or other power source was necessary -- the telephones operated on the electricity generated by the receiver/transmitter diaphragm moving under the influence of the speaker's sound waves. But sound quality wasn't very good, and it certainly wasn't very powerful!

In 1876, Bell did some further experiments outside, using stovepipe wire nailed to a fence as the conductors. This was the first, but certainly not the last, time that anyone used an "iron-wire" line. It worked well enough to prove the point over a quarter-mile transmission path and it was used extensively in the many private telephone companies well into the twentieth century. He then borrowed an existing telegraph circuit that was installed properly on a pole line and talked, first over a one-way path of eight miles, and then over a 16-mile path in 1877.

How to Connect More Than Two Telephones Together

This isn't at all difficult, either...not as long as you don't mind having everyone able to talk and to listen in at the same time! It's called a party line, and many communities were set up this way, with ten or more parties all on one line. By now, the telephone engineers had figured out that you needed some way to tell the distant party that you'd like to speak with them. They installed a ringing generator on the line: This was a device that you'd crank to make a voltage which went down the line and rang a bell at the other end. Of course, with ten people on the line, you needed to have a different set of rings for each person. And, believe it or not, this type of service was still the only thing available in a number of places in the United States into the late 1940s. The Bell System was constantly urged by the US government to take over these multiparty iron-wire telephone companies and upgrade the service to industry standard.

Source : www.moah.org/exhibits/archives/talkingwires.html

Introduction Of Switch Boards

In July of 1877, a druggist in Hartford, Connecticut installed a switchboard to connect seven doctors to his store. This was the first switchboard, which was followed by a veritable explosion of these critical items in the telephone central offices. At the beginning, boys of 12-16 years were hired to operate the boards. Because of a lack of discipline, they were soon replaced by young women who set a far higher standard. As more telephones were added to each central office, switchboard demands increased astronomically. A rule of thumb: The number of switching appearances must equal the product of half the number of phones times the total number of phones (for 50 phones, one needs 1250 appearances).

A small switchboard can be handled by one operator, who plugs connecting cords into the socket (jack) of the calling party, and a matching connecting cord into the socket of the called party.As the number of telephones in the central office increases, the switchboard must grow larger. Finally, it is so busy that one operator cannot handle all of the calls on the lines. The fix? Another switchboard, identical to the first, set right beside the first one, connected to the same circuits as the first, and worked by a second operator. Either operator can answer a caller; together, they can answer twice as many calls.

The size of a single switchboard is limited by the reach of the operator, who has to plug the connecting cords into any two sockets on the board. The number of "multiple appearances" (all the same sockets that were in the first switchboard) is set by the telephone caller activity. Historical precedent set the telephone central office size to 7,500-10,000 telephones. If more phones than that were required, a new central office was built.

Long-distance switchboards followed the same above practices. However, instead of having jacks for the subscriber telephone, they had jacks for each destination city. In 1984, the long-distance branch of the Bell System had 20,000 operators. It now has 8,000 operators, a number that is steadily being whittled down. The last manual long-distance switchboard using cords, located in Peabody Massachusetts, was shut down in September, 1996.

Source : www.moah.org/exhibits/archives/talkingwires.html