This command determines the Loop Back test status. When ON is selected, you may be able to
monitor your transmitted messages on the screen, as it is processed in the gate-array. PTT signal
is always off, so the signal won’t be transmitted. While the parameter is ON, you cannot monitor
a received message, either. Set OFF for normal communication.
4-1-5
CALIBRA command
Abbrev. CAL default: none parameter: none
Example: CAL
By using this command, the TNC enters the calibrate mode and outputs mark and space
characters alternately. This is useful for checking the transmitter or for setting transmit
deviation. Type [Q] key to exit.
In the 1200 bps mode, 1200 and 2200Hz signals are output alternately.
In the 9600 bps mode, the signals are not really alternated High/Low, but can be monitored by
observing the eye-pattern of the modulated signals on an oscilloscope.
4-2 TX related commands
To avoid conflicts with other packets, these commands are used to determine how to start
transmission. They are PPERSIST, PERSIST, SLOTTIME, DWAIT, SOFTDCD and TXDELAY.
Please cross-refer relative commands’ description, as they are closely related each other.
(A)PPERSIST is OFF
[Others transmit] [Others transmit] [Start transmit]
DWAIT DWAIT
(1) (2)
DWAIT: As another station stops transmission, DWAIT starts counting. While it is counting,
another station starts transmitting, it stops counting. When this occurs, you cannot transmit.
(1)
DWAIT: If no signal is received during the entire DWAIT period, The TNC starts to transmit.
(B)PPERSIST command is ON
[Others transmit] [Start transmit]
Slot time Slot time
(1) (2) (3) (4) (5)
blank blank hit
It’s like a slot-machine.
(1)
As others stop transmitting, it generates a random number between 0 and 255. If this
number is higher than the number set in the parameter, it is considered a “blank” and does
not transmit.