1        class Radio():	                       #1) remove parentheses (OOPS: In Python 2.4, this used to be an explict error.  As of Python 2.5 and beyond the parentheses are spurious but not technically errant)
 2            def __init__(self):                      #2) constructor must be named __init__
 3                self._powerOn = False
 4                self._volume = 5
 5                self._station = 90.7
 6                self._presets = [ 90.7, 92.3, 94.7, 98.1, 105.7, 107.7 ]
 7                
 8            def togglePower(self):
 9                self._powerOn = not self._powerOn
10                
11            def setPreset(self, ind):
12                self._presets[ind] = self._station   #3) _station is an instance variable
13                
14            def gotoPreset(self, ind):
15                self._station = self._presets[ind]
16                
17            def increaseVolume(self):                #4) Indentation of this line must be consistent with rest of the Radio class definition block
18                self._volume = self._volume + 1
19                
20            def decreaseVolume(self):
21                self._volume = self._volume - 1
22                
23            def increaseStation(self):               #5) Must use colon when starting a new block
24                self.station = self.station + .2
25                
26            def decreaseStation(self):
27                self.station = self.station - .2

    def scale(self, factor):
        for k in range(len(self._coords)):
            self._coords[k] *= factor

    def __add__(self, other):
        dim = len(self._coords)
        combined = [self._coords[k] + other._coords[k] for k in	range(dim)]
        return Point(dim, combined)

The simplest approach is to modify the togglePower method so as to read

    def togglePower(self):
      self._powerOn = not self._powerOn
      self._muted = False                 # will not remain muted after power is toggled