Meanings of electric pentacle in English

I had the bed pulled well out into the middle of the room, after which I erected the electric pentacle 'round the bed.

The candles were still burning, wan against the daylight; and behind them was the pale, glowing star of the Electric Pentacle.

I carried the things into the Grey Room, and there, in the center of the Electric Pentacle, I erected the little furnace.

Instinctively, I started sideways from it, and so plucked my hand from upon the Electric Pentacle, where-fora wickedly careless moment- Ihadplaced it.

The dawn came slowly, and presently the wan light filled all the room, and made the pale glare of the Electric Pentacle look more unearthly.