You are here: CSP Developer’s Guide: Common Channel Signaling > 14 QSIG/PSS1 > QSIG/PSS1 Licensing
The licensing QSIG/PSS1 Basic Call Signaling is based on the CSP chassis serial number.
To activate the QSIG/PSS1 feature, you must use a Product License Key, which Excel provides when you purchase the Product License. The key is unique and encrypted.
For details, refer to Downloading License Keys to the CSP in the Licensing Overview chapter in the Developer’s Guide: Overview and the Product License Download message (0x0079) in the API Reference.