Protocol Operation
Crescendo VHF Half-Duplex User Manual
Page 36 of 74
6.5.2 Answering
The Crescendo provides two options for answering dial-up calls:
Auto-answer:
In auto-answer mode, when a connection request is made the Crescendo will output a
configurable number of
RING
responses on the destination, then automatically connect.
Manual answer:
When in manual answer mode, the Crescendo will output a
RING
response on the
destination once per second until the
ATA
command is received, at which point the connection is
established. If no
ATA
command is received after the configured number of
RING
responses are
output, the connection is not established, and the dialler receives the
NO ANSWER
response. The
NO ANSWER
message is shown after the wait for carrier timeout.
6.5.3 Escape Sequence
While a protocol port is in the online state, all the data received on the port will be sent to the remote radio.
AT commands are not interpreted, and are passed over the air.
To force the radio to return to local command mode, the escape sequence is used. The escape sequence
consists of a delay greater than the escape guard time (default is one second), three escape characters (default
is „
+
‟) typed rapidly, and another delay greater than the escape guard time. As soon as the radio returns to
local command mode, it will respond with the message
OK
.
When a protocol port is in local command mode, the port can be returned to the online state by issuing the
ATO
command.
The escape sequence can be entered while in point-to-point and point-to-multipoint protocol modes. This
allows all AT commands except dial commands to be entered. When returning online, the point-to-point or
point-to-multipoint mode is restored.
6.5.4 Hanging Up
The
ATH
command is used to terminate a connection. After communications have finished, enter the escape
sequence (
+++
). The radio responds with an
OK
message. Execute the
ATH
command, and the local radio
will respond with
NO CARRIER
. The remote radio will output
NO CARRIER
as the communications link is
lost.
Hanging up can also be achieved by using DTR modes, described in section 6.5.5.