An Old Telephone Views
The communications circuits of the PSTN continue to be modernized by advances in digital communications; however, other than improving sound quality, these changes have been mainly transparent to the POTS customer. In most cases, the function of the POTS local loop presented to the customer for connection to telephone equipment is practically unchanged and remains compatible with old Pulse dialing telephones, even ones dating back to the early 20th century.
The telephone (from the Greek: τῆλε, tēle, far and φωνή, phōnē, voice ), often colloquially referred to as a phone, is a telecommunications device that transmits and receives sound, most commonly the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other. It is one of the most common appliances in the developed world, and has long been considered indispensable to businesses, households and governments. The word telephone has been adapted to many languages and is widely recognized around the world.
All telephones have a microphone to speak into, an earphone which reproduces the voice of the other person, a ringer which makes a sound to alert the owner when a call is coming in, and a keypad (or in older phones a telephone dial or no manual device) to enter the telephone number of the telephone being called. The microphone and earphone are usually built into a handset which is held up to the face to talk. The keypad may be part of the handset or of a base unit to which the handset would be connected. A landline telephone is connected by a pair of wires to the telephone network, while a mobile phone or cell phone is portable and communicates with the telephone network by radio. A cordless telephone has a portable handset which communicates by radio with a base station connected by wire to the telephone network, and can only be used within a limited range of the base station.
What turned out to be the most popular and longest lasting physical style of telephone was introduced in the early 20th century, including Bell's Model 102. A carbon granule transmitter and electromagnetic receiver were united in a single molded plastic handle, which when not in use sat in a cradle in the base unit. The circuit diagram of the Model 102 shows the direct connection of the receiver to the line, while the transmitter was induction coupled, with energy supplied by a local battery. The coupling transformer, battery, and ringer were in a separate enclosure. The dial switch in the base interrupted the line current by repeatedly but very briefly disconnecting the line 1-10 times for each digit, and the hook switch (in the center of the circuit diagram) disconnected the line and the transmitter battery while the handset was on the cradle.
An Old Telephone Images
