# Transform the UID of a 125 kHz card

To get the expected number out of a card's UID, you can transform the UID using the options described below. The way UID transformation works depends strongly on your project. In any case, however, you'll need to work with numbers on the binary level (learn more about encoding). If you'd rather leave this to us, you can order a configuration.

## Convert the card's UID into binary format

- In the entry field of the project settings form, type in the UID of the sample card.
- Below the entry field, you'll see the number in binary format.

.

## Convert the expected number into binary format

Now continue with the number you actually expect the card to return. You need to convert it to binary format, too.
To do so, you can e.g. use an
online converter such as this one*call_made*.

## Transform the UID

Now compare the binary version of the expected number with the binary UID in BALTECH ConfigEditor. Usually, the expected number will be somehow included in the UID.

To get the expected number out of the UID, you can transform the UID using the options described below. At the bottom of the screen, you can always see the final result.

We recommend you try *Cut Bitwise* first as this is often sufficient. If it isn't in your case, try the other options (and combinations of options).

### Rotate Bytewise

A byte is a block of 8 bits.
With this option, you get a **mirror reflection of the bytes**: The order of bytes is reversed, i.e the last byte is read first.
The order of bits within a byte is not affected.

### Rotate Bitwise

A bit is 1 digit in a block of 8.
With this option, you get a **mirror reflection of the bits**. The order of bits within a byte is reversed, i.e. the last bit is read first.
The order of bytes is not affected.

### Cut Bitwise

With this option, you can cut out a certain sequence of the binary UID.

- In the
*Offset*field, enter the position of the first digit of the part you want to keep. - In the
*Number in bits*field, enter the number of digits you want to keep.

To cut out the sequence in the example below, the *Offset* is 7 and the *Number in bits* is 11.

### Convert to decimal

With this option, you convert the final output back to decimal, i.e. the format of the expected number printed on the card (and shown on the screen right after the binary format). Otherwise, the number will be encoded in hexadecimal format (learn more about encoding).

### Remove fix number of trailing digits

With this option, you can remove a certain number of trailing digits from your final number, i.e. from the hexadecimal or decimal number.

### Custom length

If your final number's length is different from the expected length, specify the number of actually expected digits here.

If the number you have so far is longer, excess digits are truncated at the front.

If the number you have so far is shorter, it will be prefixed with zeros.

### Remove leading "0"-digits

If your number starts with one or more zeros, you can remove them with this option.

You're done? Here's how you can test if your project settings are working.

What to do if it doesn't work

If you just can't get out the number you expect, you have 2 options:

- Order a configuration file from us.
- Alternatively, you can work with the plain UID instead of the expected number. To do so, you need to create a new database for the host system that contains all the UIDs of the cards in your project and their corresponding card holder names. Not sure how this works? We're happy to help.