Audio devices, headset
By default, the app uses the operating system settings to use the microphone and speaker as well as the acoustic signalling of incoming calls (ringing). However, the available input and output devices can also be set differently from the operating system standard:Settings > Audio

Details about the settings are in
Audio
When using a headset, the app supports the corresponding button (named, e.g., as the Headset hook button) for ending ongoing calls (hanging up) and answering incoming calls.
Requirements: the headset uses HID standard
Important: If headset button events cause malfunctions, they can be disabled here:
Settings >
Audio >
Ignore headset button events
Details about the settings are in
Audio