A repeater amplifier boosts weak control signals on a PLC network, with noise discrimination and signal firewall protection. The AC supply voltage is filtered by a high frequency blocking filter to block external noise signals. Operating power for network signaling devices and the repeater amplifier is derived from the clean AC supply voltage. Noise discrimination and signal firewall protection are provided by amplifying and repeating only those receiver pulse signals that (a) have an analog amplitude that exceeds a predetermined analog threshold value, (b) occur during intervals that control data signal modulation is being applied to the filtered AC supply voltage and (c) occur at a frequency within a predetermined frequency band centered on the transmitted power line carrier (PLC) modulation frequency.