to a six-volt or three-cell storage battery. The negative terminals of the storage battery and dry cell set are coupled together by a short length of wire and are grounded by being attached to the engine base by a suitable conductor. The positive terminals are coupled to the two binding posts under the switch or the coil. The four points of the commutator are attached to the different units of the coil while the secondary wires run from the high

tension terminals on the bottom of the coil to the spark plugs in the cylinders. If the switch lever is placed on one contact button, the current is obtained from the dry cells. If it is swung over to the other side, electricity from the storage battery is utilized:

A typical high-tension distributor system is shown at Fig. 56. Two sources of primary current are provided, one being a six-cell, dry battery, the other a three-cell, or six-volt storage battery. The battery connections are similar to those previously shown and but a single unit coil is needed to fire all cylinders. A single

primary wire is attached to the commutator section of the distributor. The secondary wire from the induction coil is joined to the distributing terminal on the top of the distributor, from which it is delivered to the collecting terminals spaced on quarters around the outer periphery of the distributor casing by means

Fig. 58.-Complete Ford Magneto Ignition System, a Distinctive Method Found Only on This Car.

of a central distributing segment. Suitable conductors connect the distributor with the spark plugs in the cylinders.

The illustration at Fig. 57 is practically the same as that at Fig. 56, except that a distributor capable of firing a six-cylinder engine is used. If individual unit coils were to be employed, as is the case at Fig. 55, the coil box would contain six units and the

primary timer would have six contact points. The wiring would be considerably more complicated than the system outlined.

Master Vibrator Ignition Systems.-Practically the only car at the present time using the individual unit system of ignition is the Ford, the complete wiring diagram of which is clearly shown at Fig. 58, in the relation the parts actually occupy in the car. It will be observed that the induction coil has ten terminals, six of these being for the primary circuit and four for the secondary wires. The upper terminals of the coil are primary and run to the timer segments. The four secondary terminals are connected to the spark plugs as indicated, while the remaining two terminals, which are at the bottom of the coil, are joined to the magneto terminal and to the battery respectively. In the system outlined each coil has a separate vibrator.

Many Ford cars have been supplied with what is known as a master vibrator, which is a magnetic circuit breaker intended to perform that function for all of the coils. It is claimed that a device of this character produces synchronism of the ignition spark, which is not possible to obtain where four separate vibrators are used on account of some of these being tuned up faster than the others. It is contended that this makes a smoother-running engine and one delivering more power. A master vibrator unit that enjoys wide sale is of K-W manufacture and is designed especially for use with Ford cars. The method of wiring the vibrator is clearly outlined in the upper left hand corner at Fig. 59. As the vibrator unit carries a switch on its face, it has three terminals at the bottom, the center one of which is connected to one of the regular terminals of the spark coil, leaving the other one blank. One of the outside terminals of the master vibrator is coupled to the magneto, the other to a battery. The switch of the main coil is used only on one contact button, and may be left on that button, as the battery or magneto may be thrown in circuit at will by the switch on the master vibrator coil. It is necessary to short circuit the regular vibrators in order to put them out of commission. This is done by running a wire between the vibrator springs and the bridge carrying one of the contact points, as shown at the bottom of Fig. 59. Another method of short circuiting the vibrator is to

keep the points in contact by wedging a piece of wood, rubber or cardboard under the vibrator spring between the core of the coil and the vibrator. Keeping the points in contact in this manner is equivalent to short circuiting them by the wire shunt.

When but one vibrator is used the contact points must be made larger than those on the individual vibrators, because it does four times as much work. The construction of the K-W vibrator is

clearly shown, and in view of the instructions that will be given for the care and adjustment of these devices it is not necessary to describe its construction. The instructions given for adjusting the vibrator are very simple, it being merely necessary to observe if there is a space of 64 inch between the platinum contact points when the vibrator spring is held down firmly on the iron core. A gauge made of 64 inch thick steel may be placed between the contact points until the adjusting screw is screwed down to a point where the gauge can be pulled out with

out much trouble. This will give the proper distance for the armature or bottom spring to travel.

Non-vibrator Distributor Systems.-Because of the almost universal employment of electricity for lighting and starting systems, the battery ignition system has been improved materially inasmuch as the storage battery supplying the current is constantly charged by a generator. A number of systems has been devised, these operating on two different principles, the open circuit, such as the Atwater-Kent, previously described, and the closed circuit. An example of the close circuit system is shown at C, Fig. 60, and is of Connecticut design, the complete ignition system consisting of a combined timer and high tension distributor, a separate induction coil and a switch. The system is distinctive in that the timer is so constructed that the primary circuit of the coil is permitted to become thoroughly saturated with electricity before. the points separate, with a result that a spark of maximum intensity is produced. The action is very much the same as that of a magneto on account of the saturation of the winding. Another feature is the incorporation with the switch of a thermostatically operated electro-magnetic device which automatically breaks the connection between the battery and the coil should the switch be left on with the motor idle.

The contact breaker mechanism consists of an arm A carrying one contact, a stationary block B carrying the other contact, a fiber roller R which is carried by the arm A and operated by points on the cam C, which is mounted on the driving shaft. Normally the contacts are held together under the action of a light spring. As the four cams, which in touching the roller R raise the arm and separate the contacts, are 90 degrees for a four-cylinder motor, the period of saturation of the coil or the length of time the current flows through it to the battery is sufficiently long so that when the points have separated the current which has "piled" up induces an intensely hot spark at the plugs. This is an advantage inasmuch as it insures prompt starting and regular ignition at low engine speed as well as providing positive ignition at high engine speed.

The thermostatic circuit breaking mechanism is very simple.