This circuit converts BCD inputs to analog voltages. The operational amplifier must be powered according to the desired output voltage range. The circuit is from documentation from the 90s.
Any general-purpose germanium or silicon PNP transistor can be used on this receiver. The handset...
When this circuit is activated the LED flashes for a moment indicating that the function has been...
In the circuit of the figure, when pressing S1 the sound varies according to the value of R2 and...