Abstract: A cardiac pacemaker circuit for use with a stimulating electrode embedded in a patient's atrium or ventricle and a reference electrode positioned outside the heart or on the same lead within the heart. Stimulus pulses are applied by the circuit across the two electrodes, these stimulus pulses replacing evoked pulses. On termination of each stimulus pulse the amount of charge stored between the two electrodes is monitored and pulses of short duration are applied to the stimulating electrode progressively to reduce this charge over a very short time period to a level at which the intrinsic pulses of the evoked heart response can be monitored. The evoked heart response can then be used for diagnosis while the pacemaker circuit is in operation. If the stored charge was not reduced quickly then the charge would mask the intrinsic pulse and the pacemaker would have to be switched off before the intrinsic pulses could be monitored for diagnosis.

Abstract: An internal combustion engine has two cylinders (12, 14) interconnected at their head ends by a combustion chamber (20) which contains a catalyst (22). The cylinders have respective pistons (16, 18) reciprocable towards and way from the combustion chamber (20) and arranged to perform together the induction, compression, expansion and exhaust strokes. Air only or the like is freely inducted into one cylinder (12) while fuel or a fuel/air mixture is metered and inducted into the other cylinder (14) during the induction stroke. The catalyst is of a type which effects a chemical reaction to initiate combustion at a relatively low temperature so that when the fuel/air mix contacts the catalyst at the required temperature ignition takes place.

Abstract: An apparatus primarily for bird dispersal purposes at an airport has a remote control means provided for controlling operation of one or more sound emitting devices adapted to cause a detonation or emit a detonation-like sound at a required position or positions, e.g. in relation to an airport runway. The control is such that after a sound emission the device or each device is ready for further operation. Each device may consist of a combustion chamber having an outlet, the remote control means including a timer for initiating admission of fuel such as propane gas into the chamber for a pre-determined period followed by automatic ignition of the fuel/air mixture for detonation thereof. The remote control includes provision for selective operation of the devices at different positions, e.g. adjacent a runway, and also provision for selection of devices for operation at a particular runway in use or at other required locations, i.e., where there is more than one runway or location.