Voice Operated Relay Circuit Diagram
The off delay time may be adjusted by varying R3 and R4. Reducing R3 will result in a longer release time.
You could change the release time constant (C2 & R5) to say 30 seconds and use the VOX as a light switch with this delay time before turning off. Increase C2 to say 10uF and R3 to 3M3.
To make the easy adjustment, you may use potensiometer or trimpot to varying the value of resistor. You will need additional place on the PCB but it will easier for you to make some adjustment.
