H.W. Sullivan Ltd.
Factory & Showroom: Liverpool House, Middlesex Street, London, E1.
Offices: Winchester House, London, EC2
Archcliffe Road, Dover Kent CT17 9EN (1971-1987)

Largely known for the manufacture of precision electrical instruments. Initially telegraph signalling equipment, Wheatstone and Kelvin bridges and standard resistors, capacitors, and later electronic test equipment. H.W. Sullivan Ltd was incorporated into the Cambridge Instrument Co. in the 1960’s and later became part of George Kent Group and was taken over by Thorn in 1971, trading as Sullivan, part of the Thorn, Measurement and Components Division

Herbert Watson Sullivan (1856 – 1925) served a three years' apprenticeship with Telegraph Construction & Maintenance Co. Ltd. from 1870. He then joined the Eastern Telegraph Co., assisting C. V. de Sauty in the first successful duplex (simultaneous transmission in opposite directions) experiments along the 365 NM Lisbon-Gibraltar submarine cable.

Suffering from ill health at times he worked in the undersea cable lying industry for the next 20 years as electrician-in-chief and consulting engineer until starting his own business in 1897.

He saw an opportunity to manufacture and patent instruments for cable testing and telegraph signalling. The moving mirror galvanometer which he invented and developed achieved instant and worldwide recognition.

He assisted the Government in the early days of WW1, mainly in the development of wireless telegraphy which laid the foundations of an extensive connection with the Home Departments and Foreign Governments.

In 1922 he formed the business into a limited company and the Wireless & Apparatus Catalogue for Transmission & Reception for the year listed the following products:

• Accumulators and dry cell batteries
• Ammeters
• RF and Audio Amplifiers, 5 & 6 valve
• Buzzers
• Chokes
• RF Tuning units
• Reactance coils
• Condensers, Mica, glass dielectric and variable
• Grid Leaks
• Resistors
• Potentiometers & Rheostats
• R-Type Valves
• Headphones
• Valve receivers
• Transformers
• Radio Telephone transmitters, experimental and demonstration

The company manufactured a variety of standards and instruments which were used in most scientific electrical and electronic laboratories.

During the 1960s the company was acquired by Cambridge Instrument Co. which was later part of the George Kent Group and was taken over by Thorn in 1971 which also took over AVO at the same time. 

The Sullivan brand continued until 1987 when Sullivan and AVO were incorporated into Megger Instruments Limited.