The main problem with the instructions is that they do not last; and that creates a problem because every public phone operates differently from the other. The solution to this was to make the sequence as intuitive as possible.
To facilitate that, LEDs are put onto various parts of the phone (the phone line comes with a voltage of 30-40v that can run a few LEDs). The sequential flickering/ lighting up of the LEDs instructs the user.
When the receiver is picked, the coin slot lights up, indicating that the coin must be inserted.
Once the coin is inserted, the LCD display and keypad lights up, indicating that the user should punch in the number. While the numbers are being punched in, the user will be able to hear the numbers through the receiver.
If, in the middle of a call, the user has to insert another coin, the coin insert slot will light up again.
Once the call is completed, if the user has to receive any refund of coins, the coin collection slot will light up.
Instructions will be given by sound to visually impaired and will be heard through the receiver.