--- a/doc/Test-system-interface	Tue May 23 01:05:22 2017 +0000
+++ b/doc/Test-system-interface	Fri May 26 16:00:06 2017 +0000
@@ -21,8 +21,21 @@
 client in the response line.  The hint argument after the freq-meas keyword will
 be sent by the VCXO calibration program (fc-rfcal-vcxo) to tell the RF test
 system what kind of frequency offset measurement is being made, i.e., which step
-in the VCXO calibration sequence is being performed; the hint keywords remain
-to be defined.
+in the VCXO calibration sequence is being performed; see the fc-rfcal-vcxo
+source for the hint keywords.
+
+txpwr-cal-setup band arfcn
+
+This command is sent to the TSID to prepare the RF test system for the Tx power
+level calibration procedure.  The first argument after the command keyword is
+the band to be used (850, 900, 1800 or 1900) and the second argument is the
+ARFCN in that band on which the DUT will be transmitting.
+
+power-meas
+
+This command directs the RF test system to take a power level measurement
+(txpwr-cal-setup must have been performed previously) and report it back to the
+client in the response line.
 
 signal-gen-setup band
 
@@ -42,5 +55,3 @@
 signal-gen-off
 
 Turn off the signal generator.
-
-The commands for Tx power level calibration remain to be defined.