User guide

122 RealCT Direct API Developer Guide
Chapter 4: E1 Networking
Blocking a Circuit
It might be necessary for an application to stop receiving calls,
for example if the system is down for maintenance. In an analog
environment, the system can simply ignore incoming calls. In
an E1 environment using R2 line signaling, however, ignoring
calls could lead to problems with the CO.
When the far end sends a Seizure signal, the application
responds with a Seizure Acknowledgment. If the application
cannot accept calls and does not send a Seizure
Acknowledgment, the CO might consider the circuit to be faulty
and take the line out of service.
To prevent the CO from taking lines out of service, Block the
line using RHT_BLOCK_LINE. The Block signal also acts as a
Clear Back signal, terminating any incoming calls. Check with
your carrier to find out how the Block signal handles outgoing
calls. In some systems you need to terminate outgoing calls
before blocking the line. Once the application is ready to start
processing calls, call RHT_ON_HOOK to transmit an Idle
pattern on the line.
If your application tries to make an outbound call and detects a
blocked line, the line function returns error
BRKT_ERROR_CODE(IO_DEVICE). The application calls
RHT_WAIT_IDLE to detect when the circuit is Idle and can
receive calls.