{HEAD ~ A preamplifier input terminal} which is connected to 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 {TAIL ~ a terminal} carrying a reference voltage 
{ HEAD ~ A preamplifier input terminal } which is connected to 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 { TAIL ~ a terminal } carrying a reference voltage
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL 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 REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH