空调保养（Air conditioning maintenance）.doc

空调保养（Air conditioning maintenance） Electronic information science and technology Computer science and technology Electronic Information Engineering Mechanical design and automation? Electrical engineering and automation Detailed working principle of telephone set Please tell me the process of calling in detail, including two lines of telephone, the ringing tone of the switch, the modulation mode and the caller ID. Satisfactory answer Eager to ask friends, 2012-04-05 Ordinary line of two lines, although there are DC feed, there are positive and negative points, but when the ordinary telephone is not necessary to distinguish between the two lines can be arbitrarily connected. The polarity switching circuit (4 diodes) inside the telephone can guarantee the correct polarity voltage of the telephone and work normally. Ordinary telephone lines: simply speaking, feed, transmit signaling signals and language signals. The signaling signal includes: ringing signal, dial tone, DTMF, and so on. Feeding: the electrical power supplied to a telephone. Feeding voltage of telephone line in our country 48V. Ordinary telephones are fed by switches. The phone was 48 volts before it was called Ringing signal: 60-80V20Hz AC voltage rating 48V (DC), but generally will reach more than 50 points (no power, battery voltage, no load, will be slightly higher). (7.5V), ringing voltage but hook call voltage will be reduced to 10 V (DC) (this is not exactly known), a small current. The voltage is even smaller when Im talking. I dont remember 4.2 or 2 volts Telephone communication is a communication technique by which sound and electricity are converted to each other and transmitted by means of the medium of electricity. For two users to communicate, the simplest form is to connect two telephones with a pair of lines. A) when the speaker to pick up the phone microphone speech, air vibration vibration of the vocal cords, the formation of sound wave. B) acting on the acoustic transmitter, causing th