page_title: Telectronics
section_title: Development of the pacemaker
hierarchical_section_title: Telectronics / Development of the pacemaker
caption_attribution_description: Telectronics pacemaker model P6 1967 VVI
context_page_description: Telectronics Pty Ltd was an Australian company best known for its role in developing the pacemaker. It was located in Lane Cove, Sydney. In 1988 the business was acquired by Pacific Dunlop. However, legal claims resulting from the sale of faulty pacemaker electrode leads inherited by the company in acquisition of Cordis Corporation of Miami led to eventual sale of the assets of the company and Pacific Dunlop restructuring itself into Ansell.
context_section_description: Telectronics Pty Limited was incorporated in Sydney, Australia, in 1963   by technician and initial financier Noel Gray and engineer Geoffrey Wickham initially designing and manufacturing industrial and scientific instruments but diversifying into medical electronics and commencing cardiac pacemaker research in 1964. The corporate name was derived from "Television and Electronic Services", operated by Noel Gray as a sole trader from 1959 to 1964.
  
   The company made significant contributions to pacemaker technology including the first definition of the relationship between surface area of the heart electrodes & pacing pulse characteristics, the first use of integrated circuits and the first hermetic titanium encapsulation. 
  The company's first model, designated P1, was implanted in three volunteer terminally ill patients in December '64 - January'65, while 2 control samples were retained in a 37 °C. saline bath. This initial design used PNP - NPN electronics to deliver a 2.0 millisecond pulse to the Jeffcoat epicardial electrodes, and was powered by 4 Mallory mercuric oxide-zinc cells (mercury battery), all encapsulated in epoxy resin with a final dip coat of a mix of epoxy and titanium dioxide. All 3 implants failed in ability to maintain capture of the heart after periods of up to 35 weeks. These failures were later proven to be due to the excessively large surface area of the electrodes.
  The initial clinical experience led to further animal research using mongrel dogs at the laboratories of the University of Sydney medical school and at the Royal North Shore Hospital's Wellcome laboratory. In this research measurements were made of electrode impedance and pacing threshold energy over a range of pulse voltages and pulse widths, using intramyocardial electrodes of 10, 20 & 50 square millimeters surface area. The chronic measurements allowed plotting of the relationship between electrode surface area and pulse voltage/width, leading to a conclusion that an electrode area between 10 & 30 mm² was optimum in terms of energy needed when combined with a pulse width of only 0.5 milliseconds.
  
  These characteristics were incorporated in the next design to be implanted in humans, the model P4, which employed 30 mm² area intramyocardial electrodes (and later transvenous pacing electrodes), a very conservative 7.5 volt pulse and for further conservatism a magnetically operated switch which could be actuated from outside the body to change the pulse width from 0.5 to 1.0 millisecond.
   The 0.5 millisecond pulse width became the standard for later Telectronics models and became the approximate standard for all pacemaker manufacturers by the late 70's, until the evolution of externally programmable/monitorable pacemakers using digital electronics in the late 1980s. 
  
  Research also included dissection and analysis of the failure modes of explanted pacemakers of any manufacturer. Most failures were due to an internal short circuit of one of the cells of the multicell battery due to the growth of metallic  dendrites; or the result of water vapour diffusing though the epoxy resin encapsulation. The only suitable cell available at the time was the mercuric oxide-zinc cell, so the battery problems remained. In 1967 Telectronics commenced research into the technologies which could allow hermetic sealing of the pacemaker to preclude water vapour penetration and, as an interim measure contracted AWM a subsidiary of Amalgamated Wireless Australia Limited (AWA) to develop integrated circuits for the electronics.  These early integrated circuits were developed by David R Money who later joined Telectronics and later still led development of the cochlear implant for the profoundly deaf. The circuits were analogue type, housed in hermetically sealed ceramic military 'flat packs' with redundant double gold bonding of the terminations. The IC's were first used in the model P7 of 1969. 
  The first hermetically sealed models were the P8-9-10 of 1971 using titanium encapsulation with ceramic terminal insulation, developed by David J Cowdery. Bonding of the
caption: 'Demand' (VVI) model P6 1967. Epoxy encapsulation, 7 transistors, mercury battery
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