User guide

August 2001 121
Handling Incoming and Outgoing Calls
If you are using R2 inter-register signaling and you use
RHT_DISCONNECT to terminate a call, the protocol sends a
Clear Back signal to disconnect. This signal uses the same bit
pattern as the Seizure Acknowledgment signal (A=1, B=1). The
far end can not distinguish between the two signals, so the Clear
Back has no effect if the application called RHT_DISCONNECT
from the seizure acknowledgment state. The far end continues
inter-register signaling, which eventually fails because the near
end does not respond. When inter-register signaling fails, the
far end terminates the call and releases the line for future calls.
Some countries extend the CCITT R2 protocol to support the
Forced Release signal, which provides an alternate way to
terminate inbound calls. The Forced Release signal has a bit
pattern that is different from other backward signals, so it is
easily recognizable to the remote end. Use the
RHT_FORCED_RELEASE function to transmit the Forced
Release signal. This function returns an error if is called to
terminate an outbound call.
The Forced Release signal is not part of the CCITT
recommendations, and is not always supported. Check with
your carrier to find out it they support Forced Release.