# ISDN TCP parameters overview

This section describes the available parameters for ISDN Software call control. Parameter files are installed with NaturalAccess. The parameters in these files configure the TCP.

Parameter files are useful only if you are configuring the ISDNs Software in channelized configuration (as described in this manual). For more information, see Starting a TCP on a context.

Some parameters determine the amplitude, frequency, length, and pattern of the busy tone, ring tone, and reorder tone. Since the tones differ from country to country, these parameters are country-specific and must not be modified. Other parameters determine the service to request when placing an outbound call, the mode the TCP runs in, the channel direction, and the signal sending mask. These parameters can be modified for your application.