| http://www.w3.org/ns/prov#value | - When the telephone set is picked up at a time other than during the data access time, the voltage appearing across the line causes a small current to flow through the bridge rectifier circuit, through the diode in line isolator U1 where it is detected by the phototransistor in line isolator U1 and then back through the bridge rectifier circuit 147-1 to telephone lines 117.
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