diff --git a/devtimer.py b/devtimer.py
index 9dff7e5..ae010ed 100755
--- a/devtimer.py
+++ b/devtimer.py
@@ -23,29 +23,31 @@
 # Constants
 #####
 
-DEBUG = True                  # Debugging switch
+DEBUG = True                # Debugging switch
 
 # GPIO Ports And Other Hardware Constants
 
-TIME_BRIGHT = 0x0a    # Displays
-TIME_CLK = 21
-TIME_DIO = 20
-
-TEMP_BRIGHT = 0x0a
+TEMP_BRIGHT = 0x0a          # Displays
 TEMP_CLK = 12
 TEMP_DIO = 16
 
-DIMMING = 1   # How much to dim display in film mode
+TIME_BRIGHT = 0x0a
+TIME_CLK = 21
+TIME_DIO = 20
 
-FOOTSW = 6      # GPIO port to read footswitch state
-RUNNING = False # Whether or not to run the timer
+FOOTSW = 6                  # GPIO port to read footswitch state
 
 # General Constants
 
-BEEP = 15                     # Beep interval
-CALIBRATION_OFFSET = 0.003    # Compensate for program overhead in master loop
-MINUS = 16                    # Index of minus segment table lookup
-OUTOFRANGE = False            # Flag for compensating profiles when temp is out of range
+BEEP = 30                   # Beep interval
+CALIBRATION_OFFSET = 0.003  # Compensate for program overhead in master loop
+MINUS = 16                  # Index of minus segment table lookup
+TEMP_SENTINEL = 999         # Briefly appears at start, if it stays, temp measurement isn't working
+
+# Range of compensated timing
+
+TEMP_LOW=60
+TEMP_HIGH=80
 
 # Timing profiles
 
@@ -53,14 +55,9 @@
 PAPER = 1
 FILM = 2
 
-# Range of compensated timing
-
-TEMP_LOW=60
-TEMP_HIGH=80
-
 
 #####
-# Global Variables
+# Globals
 #####
 
 # These get updated by the threads that read the switches and
@@ -68,8 +65,14 @@
 # unnecessary function calls, so we make these globally RW.
 # So, shoot me ...
 
-CURRENT_PROFILE = PAPER #REALTIME
-CURRENT_TEMP = 68
+CURRENT_PROFILE = REALTIME
+CURRENT_TEMP = TEMP_SENTINEL
+
+# Operating globals
+
+DIM_BY=0             # How much are we currently dimming
+OUTOFRANGE = False   # Flag for compensating profiles when temp is out of range
+RUNNING = False      # Whether or not to run the timer
 
 
 #####
@@ -152,13 +155,21 @@
     # values that have changed more than 10 degrees since the last
     # reading, since that's almost certainly noise.
 
-    if abs(temp - CURRENT_TEMP) <= 10:
+    # At startup we want to suppress this check because we have  a
+    # sentinel value set as default for temperature that will briefly
+    # display an outrageous temperature. If it stays on, it means
+    # the temperature measurement process isn't working.
+
+    if CURRENT_TEMP == TEMP_SENTINEL:
+        CURRENT_TEMP = temp
+
+    elif abs(temp - CURRENT_TEMP) <= 10:
         CURRENT_TEMP = temp
 
     probe.close()
 
 
-# Update the store temperature every second or so
+# Update and store temperature periodically
 
 def monitor_temps():
 
@@ -174,6 +185,42 @@
         sleep(1)
 
 
+# Display current temperature
+# Negative temps are 2 digits, positive temps are 3 digits.
+# Suppress leading zeros.
+
+def show_temp(display_temp, temp):
+
+    global OUTOFRANGE
+
+    display_temp.brightness=TIME_BRIGHT-DIM_BY
+
+    if temp < 0:    # The leading digit is a minus sign
+        hun = display_time.digit_to_segment[MINUS]
+        temp = abs(temp)
+    else:
+        hun = temp // 100
+        if hun != 0:
+            hun = display_time.digit_to_segment[hun]
+
+    ten  =(temp % 100) // 10
+    if ten != 0:
+        ten = display_time.digit_to_segment[ten]
+
+    one = display_time.digit_to_segment[(temp % 100) % 10]
+    F = display_time.digit_to_segment[15]
+
+    display_temp.set_segments([hun, ten, one, F])
+    sleep(0.5)
+
+    # If we're in a compensating profile and out of
+    # temperature range, blink the time display
+
+    if OUTOFRANGE:
+        display_temp.brightness=0
+        display_temp.set_segments([hun, ten, one, F])
+
+
 #####
 # Utility Subroutines
 #####
@@ -214,43 +261,13 @@
     display_time.set_segments([d0, 0x80 + d1, d2, d3])
 
 
-
-# Display current temperature
-# Negative temps are 2 digits, positive temps are 3 digits
-
-def show_temp(display_temp, temp):
-
-    global OUTOFRANGE
-
-    display_temp.brightness=TIME_BRIGHT
-
-    if temp < 0:    # The leading digit is a minus sign
-        hun = display_time.digit_to_segment[MINUS]
-        temp = abs(temp)
-    else:
-        hun = display_time.digit_to_segment[temp // 100]
-
-    ten = display_time.digit_to_segment[(temp % 100) // 10]
-    one = display_time.digit_to_segment[(temp % 100) % 10]
-    F = display_time.digit_to_segment[15]
-    display_temp.set_segments([hun, ten, one, F])
-    sleep(0.5)
-
-    # If we're in a compensating profile and out of
-    # temperature range, blink the time display
-
-    if OUTOFRANGE:
-        display_temp.brightness=0
-        display_temp.set_segments([hun, ten, one, F])
-
-
 #####
 # Program entry point
 #####
 
 '''
   We start a perpetual thread to read the current temperature
-  and update the relevant global variable.
+  and adjust time accordingly
 
   Notice that the actual updating of the display gets run on its own
   thread as well.  That's because - on a Pi Zero, at least - it takes
@@ -268,7 +285,7 @@
 
     # Dim displays in film mode
 
-    DIM_BY=0
+    DIM_BY = 0
     if CURRENT_PROFILE == FILM:
         DIM_BY = 2