{HEAD ~ A preamplifier input terminal} which is connected to {TAIL ~ the pick up tube} by a direct current connection is connected to a control electrode of a transistor , to a terminal of a resistor and, in accordance with the invention, by a diode to a terminal carrying a reference voltage 
is connected to
{ HEAD ~ A preamplifier input terminal } which is connected to { TAIL ~ the pick up tube } by a direct current connection is connected to a control electrode of a transistor , to a terminal of a resistor and , in accordance with the invention , by a diode to a terminal carrying a reference voltage
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH