System cannot pass an unlimited number of calls simultaneously due to hardware limitations (a card cannot pass more calls then it is designed to).
By assigning a limit, we make sure that the system works without a problem with a given number of channels. By default, 246 channels are set, but this number may vary from one license type to another. To set different number of system channels:

• Login to system administration
• Navigate to 'Settings->Servers->Edit'
• Set 'Local Channels'='12' for example
• Set 'Remote Channels'='12' for example
• Click on 'Save'
• Click on 'Reload'