Powerline carrier control installation

A powerline carrier control installation comprising:

• (a) a powerline carrier control transmitter which supplies an audio frequency output voltage;
• (b) an isolation transformer having a main field inductance and having a transformation ratio higher than 1:5 fed on the primary, low voltage side by the audio frequency output voltage;
• (c) a coupling capacitor only, coupling the secondary side of said transformer directly to an a-c voltage network of given distribution system feeder a-c voltage and line frequency, the line frequency being somewhat lower than audio frequency of the output voltage;
• (d) an additional inductance only, coupling the powerline carrier control transmitter to the primary winding of the isolation transformer;
• (e) said coupling capacitor along with the main field inductance of the isolating transformer and additional inductance forming a tuned resonant circuit the resonant frequency of which is at least approximately tuned to the audio frequency, the resonant frequency of said tuned resonant circuit being determined by the capacitance of the coupling capacitor, the main field inductance of the isolation transformer and the additional inductance transmitted to the secondary winding of the transformer;
• and
• (f) the powerline carrier control transmitter being equipped to take up a line frequency backward voltage which is low in amplitude in comparison to the line a-c voltage and itself acting as a device for suppressing a line frequency feedback transmitted from the network side.