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New Contributor
Posts: 1
Registered: ‎07-24-2017

P23-DHV says 1+1=1

whay the heck is wrong with my calculator? It is brand new, but the = sign does not provide me a proper sum total for addition. It does work for multiplication and division.








Is this a setting or user error, or what? This thing should not work like a 30yo HP calculator.

Product Expert
Posts: 399
Registered: ‎02-28-2017

Re: P23-DHV says 1+1=1

Hi lscman,


Adding Machine Logic is commonly used for printing models and is preferred by bookkeepers, bankers and other members of the financial community.  That is because on Adding Machine tapes, debits and credits are clearly indicated.

Calculators using Adding Machine Logic can often be identified by the presence of two total keys.  The equal sign is employed for obtaining the results of multiplication and division ONLY.  For addition and subtraction totals, there is either an asterisk (*) or a "T".  On some units, an equal sign and asterisk may be placed on the same key and will function accordingly depending on what the previous operation was.

The total key is used at the end of an operation to total or subtotal the calculation.  When adding and subtracting, you enter in the amount and then indicate whether it is a credit or debit by pressing the + or - keys.  Please see the following addition example:

3 +
3 +

Six is displayed as the answer.  If you then press the total key, it is printed on the tape if you have printing turned on.  Please see the following subtraction example:

3 +
2 -

One is desplayed as the answer. 

To perform an addition function such as 15 + 30, follow this guide:

1.  Press 15.

2.  Press the + sign.

3.  Press 30.

4.  Press the + sign (for the result).

5.  Press the * key (for the result to be printed, if not already).

To perform a subtraction (for example 9-3=6), follow these steps:

1.  Press 9.

2.  Press the + sign (for a positive entry).

3.  Press 3.

4.  Press the - sign (for the negative entry and result).

5.  Press the * key (for the printing result/total).

To perform a multiplication function such as 3 x 5, follow this guide:

1.  Press 3.

2.  Press the + sign (for a positive entry).

3.  Press 5.

4.  Press the x sign (for the entry to me multiplied by and printed).

5.  Press the = sign (for the total and printing result).

To use the division function, follow this guide with 12 divided by 3 as an example:

1.  Press 12.

2.  Press the Division key (for entry).

3.  Press 3.

4.  Press the + sign (for the entry to divide by and printing).

5.  Press the = sign (for the result).

6.  Press the * key (for the result to be printed if not already).


If you continue to have difficulties, please contact our support group using the following link:


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