8 Line Intercommunication using 89c51 Circuit Diagram

Description

Private branch exchange
This project is aimed to make the low cost intercom system by which eight telephone lines can be interfaced with this hardware.

Main card:
In this card there is 89c51 micro controller is used. Micro controller is controller the DTMF encoder MT8870 and the Analog switch MT8816.

SLIC card:
In this card there is constant current source is used to activate the telephone. The lm339 is used to detect the hand off and hand on condition. There is same circuit are repeated because we have to interface the 8 telephone.

Summary:
When the telephone is hand on the output of the lm339 change, it is detected by micro controller that the telephone is hand on, then micro controller is make the analog channel by using the MT8816. the LM555 is used to generate the dial tone.

Circuit diagram

Click on Image And Zoom

Author: Ashad mustufa
E-mail: mustufa66@hotmail.com
Source: http://www.electronics-lab.com

Comments

Power Amplifier with voltage regulator 4 × 50 Watt TDA8588

Power Amplifier with voltage regulator 4 × 50 Watt TDA8588 The TDA8588 is a multiple voltage regulator combined with four independent audio power amplifiers configured in bridge tied load with diagnostic capability. The output voltages of all regulators except regulators 2 and 3 can be controlled via the I2C-bus. However, regulator 3 can be set to 0 V via the I2C-bus. The output voltage of regulator 2 (microcontroller supply) and the maximum output voltage of regulator 3 (mechanical digital and microcontroller supplies) can both be either 5 V or 3.3 V depending on the type number. The maximum output voltages of both regulators are fixed to avoid any risk of damaging the microcontroller that may occur during a disturbance of the I 2C-bus. The amplifier diagnostic functions give information about output offset, load, or short-circuit. Diagnostic functions are controlled via the I2C-bus. The TDA8588 is protected against short-circuit, over-temperature, open ground and open VP ...

Digital Voltmeter Circuit with ICL7107

Description. The circuit given here is of a very useful and accurate digital voltmeter with LED display using the ICL7107 from Intersil. The ICL7107 is a high performance, low power, 3.5 digit analog to digital converter. The IC includes internal circuitry for seven segment decoders, display drivers, reference voltage source and a clock. The power dissipation is less than 10mW and the display stability is very high. The working of this electronic circuit is very simple. The voltage to be measured is converted into a digital equivalent by the ADC inside the IC and then this digital equivalent is decoded to the seven segment format and then displayed. The ADC used in ICL7107 is dual slope type ADC. The process taking place inside our ADC can be stated as follows. For a fixed period of time the voltage to be measured is integrated to obtain a ramp at the output of the integrator. Then a known reference voltage of opposite polarity is applied to the input of the integrator and allowed to r...

Akira HTS 38DVD HTS – Circuit Diagram Home Theater system

Home theater system - AkiraHTS38DVD Used ICs: KA5H0165RN (SMPS control) – LC6883807 – BU1923F – BD4740G – STA505 – PS9702B – WW8721 – LA1844M Exploded Circuit Diagram Click on the schematics to magnify google.com/+GopakumarGopalan

My Circuit

Search This Blog