You can change the analog audio input and output mode.
This mode is set to [Headphone and Microphone Mode] by default.
In the Features screen, press the [
] [
] key to select [Configuration Menu], and then press the [Enter] key.
Press the [
] or [
] key to select [Audio Configuration], and then press the [Enter] key.
Press the [
] or [
] key to select a setting item from "Analog Audio Input and Output:", and then press the [Enter] key.
Press the [
] or [
] key to select [Headphone and Microphone Mode] or [Line Input and Output Mode], and then press the [Enter] key.
Press the [
] key to select [OK], and then press the [Enter] key.
When using an external echo canceller, select [Line Input and Output Mode].