Yealink SIP-T2xP Auto Provisioning Manual page 217

Parameter
phone_setting.backlight_time =
(not applicable to SIP-T21P , SIP-T20P and SIP-T19P IP
phones)
Permitted Values
1-Low
The default value is 1.
It configures the backlight time (in seconds).
For SIP-T28P/T26P/T22P IP phones:
0-Always on
1-Always off
15-15s
30-30s
60-60s
120-120s
300-300s
0, 1, 15, 30, 60, 120,
300, 600 or 1800
600-600s
1800-1800s
The default value is 30.
For SIP-T4X/CP860 IP phones:
0-Always on
15-15s
30-30s
60-60s
120-120s
Descriptions
Settings->Preference->Backlight Time
(seconds)
Appendix
Web Setting Path
207