Top key is used for displaying [Time] → [Date] → [Temperature 0] → [Temperature 1] → [Voltage] → [Cycling Display].Bottom key cycles the settings (top key then increments their values) between:MinuteHourDayMonthYear0.0 u - Voltage display error adjust, in 0.1V steps, up or downAc: 0 - Temperature 0 error adjust, -5 to +5°C.AC: 0 - Temperature 1 error adjust.dd: 0 - Changes display cycling options [dd: 0] time + temp 0 + temp 1 + volts [dd: 1] time + temp 0 + temp 1 [dd: 2] time + temp 0 + volts [dd: 3] time + voltsdF: 1 - display dwell time, 1 - 9 seconds (Do not set to " 0 ")LL: 1 - display Light Level 1 is darkest, 3 is brightestAL: 0 - Auto Light level 0 OFF 1 ON (level 1 at 19:00, level 3 at 07:00)Returns to run state, parameters saved.The RT clock operates during IGN PWR OFF from a 3V lithium cell. And yes, it does lose time; one ✡ demerit for that.NOTE: Even though both the T0 and T1 return pins ohm out as being the same connection point, do not use a three wire common return cable to extend the sensors. Each high impedance (~3kohm at room temperature) sensor needs its own two wire path back to the unit or the temperature display will be dodgy.