default or selected kernelversion does not have config value CONFIG_HISAX_HFCS.
Result is shown for kernelversion 6.9.9

HFC-S based cards

configname: CONFIG_HISAX_HFCS

Linux Kernel Configuration
└─>Device Drivers
└─>ISDN support
└─>Old ISDN4Linux (deprecated)
└─>Passive cards
└─>HFC-S based cards
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
This enables HiSax support for the HFC-S 2BDS0 based cards, like
teles 16.3c.

See <file:Documentation/isdn/README.HiSax> on how to configure it
using the different cards, a different D-channel protocol, or
non-standard IRQ/port settings.