With the rapid development of the communication industry, the use of telephones has become increasingly popular. In order to meet the modern rhythm and quality of life, the author has designed a new type of telephone. After installing the telephone, you can dial the remote control of various household appliances, such as cooking, cooking, washing, recording, video recording, etc. This design includes two major parts of hardware and software. The hardware part is mainly composed of ringing circuit and several parts. The software mainly decodes by assembly language programming to control the household appliances. This design selects single-chip AT89C5I and LH1240, LH1062, TBA820M, HA324, 4N35 and other integrated blocks, with high degree of integration and superior performance. By setting up dialing, each time you can control one household appliance, you can also control a group of household appliances or multiple sets of household appliances. At most, you can design the hook switch of the hardware part at the same time: it consists of a normally closed contact and a normally open contact.

The hook spring completes the on/off task of the call circuit and the ringing circuit and the outer line 1 in the telephone, and is actually an automatic switch. It utilizes the gravity of the handle and has two states: off-hook and on-hook. Turn on the call loop when you pick up the phone, and turn on the ringing circuit when you hang up.

Ringing circuit: mainly composed of two-tone electronic ringing circuit LH1240 and related circuits. The function of the ringing circuit is to receive the call signal, that is, to convert the 25 Hz ringing current sent by the switch into a direct current, and then generate two alternating signals with different frequencies, and drive the speaker to sound after being amplified.

Polarity protection circuit: It consists of a diode bridge circuit. Its function is to send the DC and AC signals sent by the switch to the relevant circuit of the telephone, and to feed the call signal and the send signal to the outside line.

Dialing circuit: consists of the special serial block LH91215C, the numbering control circuit, the numbering output circuit and the keyboard. The function is to send the phone number of the keyboard into the corresponding pulse or dual-tone multi-frequency signal to the outside line. At the same time, a quiet noise signal is emitted to eliminate the noise generated in the receiver when dialing.

Call circuit: The handle call circuit selects the typical application circuit of integrated circuit LH1062, which consists of the sending circuit, the receiving circuit and the canceling side circuit. Its main function is 2/4 line conversion, eliminating the sidetone, receiving and transmitting signal amplification, etc. . The hands-free calling circuit is composed of an integrated circuit HA324 and a small power integrated circuit TBA820M and peripheral devices. The circuit uses the two sets of operational amplifiers of the HA324 to perform switching control for transmission and reception, and amplifies the transmission by a set of operational amplifiers of the HA324, and the received portion is amplified by the TBA820M to push the speaker to pronounce.

Handle: It consists of a microphone and a receiver. The microphone is an acoustic-electrical conversion device that converts an acoustic signal into an electrical signal, and the receiver is an electro-acoustic conversion device that converts an electrical signal into an acoustic signal.

Automatic pick-up machine circuit: mainly composed of photocoupler 4N35, audio phase-locked loop circuit 1M567 and peripheral circuits.

The other party calls, the ringing signal is applied to the photocoupler 4N35, and the 4N35 outputs a low level control telephone to connect the electronic door, so that the phone automatically picks up the phone. The audio phase-locked loop circuit LM567 mainly performs the dial tone detection function. When it detects that the telephone line is a dial tone, the control phone keeps the off-hook state; when it detects that the phone line is busy, the control phone automatically shuts down.

Decoding circuit: mainly composed of dual tone multi-frequency decoding integrated circuit MT8870 and its peripheral circuits. The role of MT8870 is to amplify, filter and separate the different audio signals on the line, and then convert them into binary BCD code lock output.

Decoding circuit and control circuit: mainly composed of single-chip AT89C51, triode, relay and peripheral components. The dual audio signal sent by the telephone is decoded into a binary BCD code by the integrated block MT8870 to be sent to the P3 port of the single-chip microcomputer. After being programmed by the internal program of the single-chip microcomputer, the related pins of the single-chip P0, P1, and P2 outputs a high level, thereby correspondingly The triode is saturated and turned on, causing its load-relay to be energized, thereby controlling the corresponding household appliance to be powered on and starting to work.

2 The software part of the design part mainly controls the high and low potentials of the P0, P1 and P2 ports of the single chip AT89C51 through assembly language programming to control the household appliances. The basic principle is based on the NS flow chart of the dialing remote control home appliance decoding software based on the telephone. The number is the reset switch. It can be seen from the figure. If the dialed number is 10, all the 8 household appliances controlled by the P0 port work, if the dialed number is 20 Or 30 sets of 8 household appliances controlled by P2 and P3 respectively work. If the dialed number is any one of 11-18, the corresponding one of the 8 household appliances controlled by the P0 port works. If the dialed number is any one of 21-28, the 8 households controlled by the P1 port The corresponding one in the electrical appliance; similarly, if the dialed number is any one of 31-38, the corresponding one of the eight household appliances controlled by the P2 port works. If 10, 20, and 30 numbers are successively dialed, 24 household appliances work at the same time.

3 Conclusion Through the principle analysis and the test of the circuit and the debugging of the machine, the following conclusions can be obtained.

3.1 The indicators of the telephone are in line with the national standard, objective transmission, reception, side tone equivalent ringing level > 70dB automatic off-hook, shutdown circuit sensitive, superior performance.

3.2 Programming through assembly language based on single-chip AT89C51 control of household appliances has achieved good results by setting up dialing, each time you can control a household appliance,

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