Sound Card / Microphone CMOS Switch with Monitoring

The purpose of this box is to seamlesly switch between the PC sound card and the hand microphone. While the PTT button on the MIC is not depressed TCVR is driven by the sound card. When PTT is depressed it is driven by the MIC. If you need to fully control TCVR by the PC (such as a software voice keyer) it is necessary to control PTT of the TCVR as well. I use WinKeyer 3 which is present and wired anyway. This way the software voice keyer fully controls transmission. However, I can take the MIC into hand and start speaking at any time.

For clicking-free switching the CMOS switch 4053 is used.
To be able to monitor what the sound card plays a small amplifier is incorporated with the output to a speaker (LM386). When the PTT is depressed the amplifier is muted.
The project is similar to previously made
voice keyer in many respects.
The device doesn't need any power supply. It is supplied by 8V that is available on the MIC connector (all Icom TCVRs).

Prototyping stage using a bread-board.

Top view with the cover removed.

The bottom panel. Mind the chokes on the connector.

The front panel. Mind the chokes on the connector.

The bottom view with the holes (speaker).

Fully QRV.




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