Telephony Circuits and DTMF Circuits

Posted on Feb 7, 2014

9-line telephone sharer This circuit is able to handle nine independent telephones (using a single telephone line pair) located at nine different locations, pdf file Bidirectional telephone line simulator without using telephone lines, couple, test and demonstrate all types of telephone equipment such as: answering machine, modem, fax, call record

Telephony Circuits and DTMF Circuits
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er, call diverter, extension ringer, telephone ring booster, security autodialler etc. Couple modem equipped PCs for gaming or testing of communications software Cordless phone frequencies cordless phones are still analogue and use the frequency from 30-50MHz. The signal is FM-modulated and can easy be picked up with any FM-receiver DTMF Generation with a 3. 58 MHz Crystal DTMF generation consists of selecting and combining two audio tone frequencies associated with the rows (low band frequency) and columns (high band frequency) of a pushbutton touch tone telephone keypad, pdf file DTMF Generator The MV5089 is fabricated using ISO-CMOS high density technology and offers low power and wide voltage operation. An inexpensive 3. 58MHz TV crystal completes the reference oscillator. From this frequency are derived 8 different sinusoidal frequencies which, when appropriately mixed, provide Dual-Tone Multi-Frequency (DTMF) tones, pdf file DTMF tone decoder with LCD display this project displays telephone numbers decoded from tones. A microphone picks up the tones, a preamplifier boosts the signals, an SSI-202 DTMF chip decodes the tones, a Basic Stamp acts as an interface to an LCD display and also provides "RS-232" serial output Telephone Line In Use Indicator This document presents a design for an electronic circuit which connects to a telephone line and provides a visual indication of whether or not the line is in use, so that...

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