User guide

74 RealCT Direct API Developer Guide
Chapter 3: T1 Networking
Sending and Detecting Winks
The Wink Start and Double Wink Start protocols use wink
signals as part of their call setup process. In order to perform a
wink, the channel must be in the on hook state, transmitting the
appropriate bit pattern for that protocol. An off hook pattern is
transmitted for the duration specified by
RDG_LOCAL_WINK_DUR, followed by the on hook pattern for
the duration specified by RDG_LOCAL_WINK_GUARD_TIME.
In the Wink Start protocol, the driver uses the protocol file to
automatically send or detect the wink that acknowledges line
seizure. In the Double Wink Start protocol, however, a second
wink must be sent by the receiving end after receiving all digits
and before answering. Since the timing of this second wink is
determined by when the application finishes receiving digits
and not by the protocol, the driver cannot send the wink
automatically. Use the RHT_SEND_WINK and
RHT_WAIT_WINK functions to send or receive this second
wink in the Double Wink Start protocol. Add a pause after the
second wink in the Double Wink Start protocol so the CO can
distinguish between the wink and the answer signal. Check
with your carrier provider for the duration of the pause.
In order to detect a wink, the channel detects an off hook
pattern on the line for a period of time within a range defined by
RDG_REMOTE_MIN_WINK and
RDG_REMOTE_MAX_WINK. RHT_WAIT_WINK returns an
error if the wink duration does not match the specifications.
Unlike the wink detection performed when seizing a line,
RHT_WAIT_WINK does not set a maximum time for the wink
to be received. It waits until it detects a wink, a signaling error
occurs, or the function is stopped externally.
If the application needs even more control over a Wink Start or
Double Wink Start protocol, it can load the Immediate Start
protocol file instead and manage sending and receiving all
winks manually.