Introduction:
If you are having issues registering or connecting calls on an unsupported 3rd Party SIP device, it may be due to the SIP User Agent Filter built into MaxCS. The filter prevents the system from processing calls from unknown SIP devices, which have the potential to cause issues. Typically, MaxCS will respond with a 486 Busy Here message if a connection is blocked by the filter. You may disable the filter by performing a simple registry edit explained below if you would like the system to accept SIP connections from any device. 


To Disable SIP User Agent option:

1. Open the registry editor and go to: HKEY_LOCAL_MACHINE\SOFTWARE\AltiGEn Communications, Inc.\AltiWare\Service Providers\SIPSP

2. Add a new key, "UserAgentFilter" as a DWORD. Set the value to 0. 

3. Reboot the machine for the new setting to take effect.