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+R&S CMU200 is the RF tester used for production RF calibration of FreeCalypso
+GSM devices.  The CMU200 can be operated in three ways: manually via the front
+panel, programmatically via GPIB and programmatically via SCPI commands over
+RS-232.  GPIB is the industry standard, but for FreeCalypso the Mother has
+adopted the RS-232 control interface method instead in order to avoid the
+exotic hardware and equally exotic drivers and libraries required for GPIB:
+using the RS-232 interface requires absolutely no special hardware or drivers
+or libraries, just userspace C code without any dependencies talking to a
+serial port just like we do when communicating with Calypso target serial ports.
+
+Initialization commands
+=======================
+
+Our Test System Interface Daemon for the CMU200 will issue the following SCPI
+commands to the instrument on start-up:
+
+*SEC 0
+*RST;*OPC?
+SYST:NONV:DIS
+SYST:REM:ADDR:SEC 1,"RF_NSig"
+SYST:REM:ADDR:SEC 2,"GSM900MS_NSig"
+SYST:REM:ADDR:SEC 3,"GSM1800MS_NSig"
+SYST:REM:ADDR:SEC 4,"GSM1900MS_NSig"
+SYST:REM:ADDR:SEC 5,"GSM850MS_NSig"
+
+VCXO calibration
+================
+
+When commanded to prepare for VCXO calibration, our TSID will command the
+CMU200 as follows:
+
+*SEC 2
+RFAN:CHAN 40CH
+RFAN:TSEQ GSM5
+
+Command to read frequency offset:
+
+READ:MOD?