dramrattan
Member
Hi,
The circuit diagrams are used to describe a device that interfaces a microcontroller to a telephone line, and is capable of receiving and decoding a series of DTMF signals, and to execute commands received this way.
In the few diagrams attached, i have understood the use and choice of the values of all the passive components except those connecting between DT (seen in diagrams connecting "Astable Multivibrator and "Ring Detection") of the Astable multivibrator to the Secondary of the Transformer. Namely, Q1, R5, R6, R7 and C3. It seems that R6 and R7 serves as a voltage divider for the signal from the Astable Multivibrator to produce a voltage to turn on the Transistor Q1, but i don't know for what purpose.
Also there's a resistor connected from pin 4 to ground of the multivibrator as well as a capacitor to ground from pin 5. Why are these two components used?
I read articles on the 555 timer and understand the use of R11, R12 and C7 in determining the turn on/off times when a trigger pulse is received at the input but don't understand the use of R13 at pin 4 and C6 at pin 5.
Could anyone please help with this?
The circuit diagrams are used to describe a device that interfaces a microcontroller to a telephone line, and is capable of receiving and decoding a series of DTMF signals, and to execute commands received this way.
In the few diagrams attached, i have understood the use and choice of the values of all the passive components except those connecting between DT (seen in diagrams connecting "Astable Multivibrator and "Ring Detection") of the Astable multivibrator to the Secondary of the Transformer. Namely, Q1, R5, R6, R7 and C3. It seems that R6 and R7 serves as a voltage divider for the signal from the Astable Multivibrator to produce a voltage to turn on the Transistor Q1, but i don't know for what purpose.
Also there's a resistor connected from pin 4 to ground of the multivibrator as well as a capacitor to ground from pin 5. Why are these two components used?
I read articles on the 555 timer and understand the use of R11, R12 and C7 in determining the turn on/off times when a trigger pulse is received at the input but don't understand the use of R13 at pin 4 and C6 at pin 5.
Could anyone please help with this?
Attachments
Last edited:
