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Radio Protocol Support
17
SRL-35 Operator’s Manual
P/N: 1003224-01
In order to match the operation of the radio modem to the user data, the Pause length parameter can be
adjusted on the programming menu. It may have any value between 3 and 255 characters. The default
value is 3 characters.
TX Delay
The radio modem can be configured to delay the beginning of a radio transmission by 1...65000ms. This
function can be used to prevent packet contention in a system, where all substations would otherwise
answer a poll of a base-station simultaneously. During this delay data sent to the radio modem is buffered.
Although the priority setting is
RX
, radio modem is prevented to change over to receiving mode during the
period of the TX delay. If this function is not needed, the delay time should be set to 0 ms.
Testing
The radio modem can be switched to the
Test Mode
, where it will send a test packet on the radio channel.
The test packet is a normal data transmission, which can be used, for example, when directing antennas
during system installation.
When the test packet transmission has been switched on and saved by using the Programming Mode, the
transmitting radio modem needs only a power supply and an antenna.
If the channel spacing of the radio modems is 25 kHz, it is recommended to use 38400 bps as a serial data
speed of the receiving radio modem. In the case of 12.5 / 20 kHz channel spacing the data speed of 19200
bps is recommended.
There are two
Test Modes:
Short Data Block Test
In this test mode the radio modem sends a short test string, which is preceded by a consecutive number,
and it ends to the line feed character. The short data block is repeated continuously after 1 second break.
Short data block test is suitable for running data communication tests. Error-free reception of data can be
monitored using a suitable terminal program (TRU).
•
The absolute time of Pause length is depending on the serial port settings. For example, 1
character is ~1.04 ms at 9600 bps / 8N1 (10 bits).
•
The maximum absolute time is always 170 ms independent from the value of the Pause
length given in the set-up.
•
An increase in the Pause length increases the round trip delay of the radio link
correspondingly; this is due to the fact that the radio channel is occupied for the time of the
Pause length after each transmission (the time it takes to detect a pause). If this is not
acceptable, the TX delay setting may also be useful in special cases.
Refer to “Changing Parameters Using a Terminal Device” on page 58 to enable test mode
"ON" (Option 9) using a terminal program.
