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