Please follow the steps below for your particular Iwatsu system.

From the Operator DSS when idle:

Press [ICM] + [FEAT] + [6] + [4]
Enter the time [HH MM] using the 24 hour military clock
Press [SPKR]

From the operator only when idle:

Go off-hook and press [FEAT] + [SPKR] + [3]
Enter the time [HH MM] using the 24 hour military clock
Go on-hook

From the Master KT only, when idle:

Go off-hook and press [FEAT] + [#] + [2]
Enter the time [HH MM] using the 24 hour military clock
Go on-hook