Instructions for the Desktop Calculator with earphone:

Below the display you will feel a slide switch.  Slide it as far left as possible, this turns the volume/speech OFF.  The central position of this switch is LOW VOLUME and the far right position is MAX VOLUME.  To the right of this slide switch there are three smaller buttons. From left to right they are; RESET, which resets the complete calculator including the memory.  The next button is U/D; which allows the answer to be spoken as a unit or individual digits.  The furthest right button is the ARO button; this allows only the calculated result to be announced without hearing each key entry.

Essentially  the calculator works in the same way as a standard calculator.  

Layout of the calculator:

The number buttons are located to the left of the keys.  The first column of buttons from the left are: 0, 1, 4, 7 with seven being at the top.  The second column is: Decimal point, 2, 5, 8.  The number five button has a raised section on it for ease of use.  Using this you can locate the positions of the surrounding numbers.  The next column continues numbers 3,6, and 9 and has the EQUALS button at the bottom.  The fourth column has the MULTIPLY, SUBTRACT and ADD buttons, with the add button being larger than the other two.  The next column has DIVIDE, PERCENTAGE and REPEAT (REP.).  The repeat button is again larger than the other keys in this column.  
The next section has smaller buttons.  These are as follows: the first column from the right: (top button) MC this is used for Memory clear.  The following button; M+ which is used for Memory plus.  Third button: AC which is the All Clear button.  Below this button you will feel a slightly larger one; this is ON.  
The column of buttons next to this consists of the following:  MR this is Memory Recall. The next is M- which is Memory minus. Then CE; this clears your last entered number.  Below this button is OFF, which turns the unit off.

USING THE EARPHONE:

For safety reasons have the volume on low when first using the earphone function.  To use the earphone function, plug the earphone into the socket located to the left of the display.  You can then continue to use the unit in the same way as before.

BATTERY REPLACEMENT:

Located on the back of the unit in the centre of the raised section, you will feel a small textured area, this is the battery compartment door.  Use this textured area to open the door, by sliding it downwards towards the flat of the unit.
Once open the door will come away and the batteries will be exposed.  Once you have removed the old batteries you will feel two springs inside the compartment.  
Place the new batteries in with their flat ends pushed up against the springs.  Replace the battery compartment door, by sliding in the opposite direction to before.