Справочник Пользователя для Kenwood TK-3130

You can set the display illumination to remain off, remain on,
or turn on when you press any key other than the PTT switch
(auto).  When set to auto, the lamp remains on for 5 seconds
after pressing a key before turning off again.

To turn the display backlight ON:

Turn the transceiver power OFF.

Press and hold the MENU key while turning the
transceiver power ON (for 1 second).

Press the 

▲

 or 

▼

 key to select “LP”.

Press the MENU key to select “LP-OF” (lamp off), “LP-On”
(lamp on), or “LP-A” (lamp auto).

Press the PTT, MON, or CAL key to exit Menu Mode.