| 摘要 |
Consists of a street plate 1, telephone 2, power supply 3 and door openers 4 connected together with two wires, connecting the transformer 48 to the telephone 2 with a bridge rectifier 47 to supply direct current to the whole circuit, using the integrated circuit 5 and the integrated circuit 17 as a low frequency amplifier and the stabiliser integrated circuit 50, to actuate a relay 33 through the transistors 13 and 15 and through the transformer 20, completing a circuit with the street plate 1 through the bridge rectifier 34 and by means of the transformer 8, reaching the street microphone 35 and loudspeaker 21 through the transistors 38 and 39, in communication with the loudspeaker 27 and the microphone 29 of the telephone handset 2, in order to actuate the door openers 4, by means of operating the entry pushbutton 6 from the telephone 2. <IMAGE>
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