D2, D3 and D4 are all HIGH.
A short call with back light on for under 20 seconds will turn the socket ON and then OFF alternately (ie toggle). So on startup the first call you make in this mode will turn the socket ON and the second short call will turn the socket OFF.
If you forget whether the socket is ON or OFF just make a call which turns the backlight ON for over 20 seconds and under 30 seconds. The socket will be turned OFF no matter what its previous state.
See Mode 1 for explanation of backlight timings.
See AUTOMATIC OPERATION OF SOCKETS.
This Mode is ideal for turning ON the Sockets with an automated text.