User's Manual

System operational description
November 24, 2004 3
Slave-to-Master messages are called Data Transfer Sequences (DTS),
used for data retrieval, seismonitor and collecting test results.
Figure 3
Typically, NCS messages are transmitted every 50 ms. In reply to an
NCS message, the LAUR transmits a DTS message (1.5 to 40 ms long).
The LAUR does not transmit its DTS until and unless its clock is locked
onto that of the LRU.
LAUR frequency management
NOTE: The available frequency band depends on the regional settings
chosen by the user when installing software on the HCI workstation and
on the handheld terminal. For compliance with Canadian and US
communications regulations, the frequency band is limited to
respectively:
• Canada: 217 to 218 MHz and 219 to 220 MHz.
• USA: 216 to 217 MHz and 218 to 219 MHz.
The LAUR uses QPSK modulation @ 256 kbps, or 16 QAM @
512 kbps (for transmission only), or DQPSK modulation @ 1024 kbps.
The RF transceiver in the LAUR unit uses a single 2-MHz band for both
transmission and reception. That band is selected between 216 MHz and
249 MHz using the “Center Frequency” parameter.
Within the 2-MHz bandwidth, you can choose which channel(s) to use
for NCS and DTS messages, by specifying:
•a Control Channel Frequency for NCS messages,
•a Data Channel Frequency for DTS messages.
NCS DTS NCS DTS
(50 ms)
(50 ms)
Radio frame
time