Muirhead mercury dipper relay

Lodge-Muirhead Transmitting Buzzer

This device used a cross-coupled pair of telegraph sounders to vibrate a copper electrode at about 10Hz. The electrode dipped into a mercury bath, making and breaking the induction coil primary circuit at a definite frequency and giving consistent sparking. Made in 1903 by Muirhead & Co, Westminster, for the Lodge-Muirhead Wireless Telegraphy Syndicate.