According to KDC-MP342U KDC-MP242U - Kenwood Owner’s Manual, here’s how to set the Demonstration Mode:
1) Enter Menu mode:
Press the Search button for at least 1 second. “MENU” is displayed.
2) Select Demonstration mode:
Press the [FM+] or [AM–] button.
Select the “DEMO” display: DEMO ON (The Demonstration mode function is on) or DEMO OFF (Exit Demonstration mode (Normal mode))
3) Set the Demonstration mode:
Press the [AUD] knob for at least 2 seconds.
4) Exit Demonstration mode:
Press the Search button.
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