Controlling the B-Channels • 9-5 •
The H.110 Basic Rate ISDN Board
message. Like the “ST” message, the “SL” message has a character
specifying the bank followed by sixteen characters that act as arguments for
each of the ports. For the “SL” message the choices are “2” if only “LC”
messages are to be used for call control, “3”, “A”, “D”, “E”, or “N” if
“D” messages are to be used. The “A” is used for AT&T Custom
switches, “D” for DMS-100 or 5ESS switches with National ISDN
software, “N” for other National ISDN switches, and “E” if “D” messages
are used and the port is being used for CACH EKTS. The default is “2”.
The port type and protocol level information can be stored in the EEPROM
to be loaded automatically on power up or a restart. See Section 4.3 for
details.
9.4 Using the “C” Commands
The B-channels on the H.110 Basic Rate ISDN Board can be set to
provide full-duplex connections as well as half-duplex connections in either
direction. They can also be used to send DTMF and call progress tones
as well as provide DTMF and energy detection.
Changes in the B-channel state are reported in state change messages.
These consist of the letter “S” followed by a letter indicating the change,
the B-channel number, and an optional information character. An example
is the message SI00 which indicates that B-channel 00 has returned to the
idle state.
9.4.1 Making a Connection
A two-way connection can be made with a port using the Connect
Command “CC”. This command takes the form CCxxssttaabb, where
xx is the B-channel number, sstt is the destination stream and timeslot and
abb is the source stream and timeslot to be connected to. As an example,
the message CC0001020304 would connect B-channel 00 with timeslot 2,
stream 1 being the transmit timeslot and timeslot 4, stream 3 the receive
timeslot. Note that if a transmit timeslot had been reserved for the port
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