Friday, December 27, 2013

FM Radio Station Mute Function Part 14

Radio Station mute function schematic

This circuit shows details for adding a mute function to the FM radio station. A switch will mute the microphone. When muted, the LED will stay lit.

Microphone Mute Function with LED monitor
When the DPDT switch is in a normalized position, the electret microphone is active, the LED is not connected, and broadcast takes place. When switched, the microphone cuts out, resistor R2 is connected to replace the microphone, and the LED lights. A carrier signal continues to broadcast but there is no sound. The LED is on a separate circuit and does not interfere with the microphone.
The microphone resistance is measured at 1.37 ohms (when not in the circuit).

Note: On the schematic, replace the text SPDT with DPDT.

FM Radio Station Part 5 Index