code: def set_enable(self, on, channel=1):
          
          if isinstance(channel, str):
              cmd = "OPALL %d" % int(on)
          elif isinstance(channel, int):
              cmd = "OP%d %d" % (channel, int(on))
          self.write(cmd)
docs: channel: 1=OP1, 2=OP2, 3=AUX, ALL=all channels