
When apartment, Villa or house have two entrances, it is not always clear where to call. Electrosonic, which tells of the Bulgarian journal “Radio Television Electronics”, rid us of this inconvenience. When you press the button S2, relay K1 cambiocorsa their contact close. Simultaneously, lamp H2 lights up. Call H3 will beep until until the capacitor C1 is not charged up to the supply voltage. To signal again, the button S2 is released, and the capacitor C1 is discharged through the winding of the call. H2 lamp continues to burn as long as the supply circuit of the relay K1 will not open with button S3.
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