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broken easily. If you look closely, you can see wires poking out of the board. The wires are soldered to the terminal legs. If you break one of those wires, man are you dead!

TELEPHONE HOOK SWITCH

Every time you talk over a line, you always need to disconnect. The most simple thing to do is to let the handset sit down. While sitting down, the handset can give force to a spring loaded operating arm, which is connected to a number of switch contacts. When this happens, the phone disconnects.

THE PHONE RINGER

Once a call has been dialed through, the telephone of the person being called must be given some kind of signal to let him/her know that he/she has been called. This is when the telephone rings. This type of signal is generated using an alternating current somewhere between 90 to 220 V with a frequency of 30 Hz.

But what if you have 5 or 6 phones connected on a party line? How can you signal one telephone to ring? The answer is by frequency selection. Older telephones had a different capacitor and ringer coil impedance values. It was these small differences that made the bell select one frequency.

For example, if you have 5 telephones on one party line. If a call came through for line 1, the central board would send 10 Hz (this is a guess) signal to the party line. Line 1 would ring and all the others would remain quiet. If the call was for line 5, the central board would send a 50 Hz (this is also a guess) signal so that only line 5 would ring.

The phone rings by applying voltage where needed, a resonant circuit is made. The xx Hz signal would make a magnetic field around a device called the hammer. The hammer is attracted and then repelled by the constant changing of the magnetic field. If two gongs were placed on either side of the hammer, the hammer would strike each gong successively.

Other phones can use a one gong system. This system is like the two gong system, but more compact. Due to the compact in size, this ringer is perfect for small wall phones or such.

THE ROTARY DIAL (PULSE)

A rotary dial creates equally spaced make -- and -- break pulses according to how far the plastic dialing plate goes. A good description of a dialing plate is like this: it has regularly spaced holes to dial with and a metal object called the finger stop. That makes the number you want to go to as easy as 1-2-3. Each hole in the wheel represents one number 1 through to 10.

By using some small gears and a device that times the velocity of the return of the finger wheel after you have dialed, the internal switches are opened and closed at a rate of 1 pulse per second. The number of pulses created is determined by how far the finger wheel has gone around before being stopped by the finger stop. Let's say that you dial the number 5, that means the internal switches open and close 5 times before the finger stop stops it.

During the dial, a second set of switches remain closed and stay that way for the entire time that you are dialing. The purpose for this second set of switches is to keep the telephone receiver short for the whole dialing period. If this switch was not there, you would hear loud and frustrating clicks in the receiver.

TONE DIALING

There is also an alternative to the pulse dial, that is the tone dial. Phones that use tone dialing are made with a piece of machinery that makes tones on the phone line. These tones are本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。