Motorola AP-51XX - Manual (Page 235)

Configuring Access Point Security 6-17
5. Configure the WEP 64 Settings or WEP 128 Settings field as required to define the Pass
Key used to generate the WEP keys. These keys must be the same between the access point
and its MU to encrypt packets between the two devices.
Pass Key Specify a 4 to 32 character pass key and click the Generate button.
The pass key can be any alphanumeric string. The access point,
other proprietary routers and Motorola MUs use the algorithm to
convert an ASCII string to the same hexadecimal number. MUs
without Motorola adapters need to use WEP keys manually
configured as hexadecimal numbers.