The Philbrin ignition system consists of a specially designed contact maker and interrupter, a distributor mounted on the same shaft, a nonvibrating heat and moisture proof coil, an armored heat, moisture, and puncture proof condenser, and a special Duplex switch.

Fig. 80 shows an illustration of the Philbrin contact maker which operates in this manner. The cam A strikes against the end of the plunger B and forces the points together at C, and holds the contact for approximately three and one-half degrees of the revolution of the cam. The spark occurs simultaneously with the separation of the contact points. The contact maker has but one adjustment; that of the adjustable contact screw, which is in direct line with the contact plunger. The contact points are brought together gradually by the surface formation of the cam. When the point of ample saturation of the coil is reached, the breaking of the contacts is instantaneous. The duration of the spark is in proportion to the speed of the engine, but breaking of the points is always instantaneous and entirely independent of the engine’s speed thereby producing the required spark at all speeds without any spark lag.

Fig. 81 shows the distributor blade mounted over the contact maker. The distributor blade is so arranged that it clears the spark plug lead terminals in the cover by a slight margin, and does not make actual contact, thereby eliminating all friction due to such contacts.

Operation.—Turning on the switch sets up a low tension current in the coil and primary wire coil when the contact points close. The sudden breaking of this current causes demagnetism of the core and the primary coil to set up a high tension current in the secondary coil. This current is led to the distributor blade and passes to the spark plug terminals as the blade comes in contact range.

The Philbrin high frequency system uses the same coil and distributor as the single spark system. But as the circuits of the two systems are entirely distinct and separate, they do not conflict with each other. The high frequency system has its own condenser and interrupter located in the switch case, and supplies a continuous flow of sparks.

Fig. 82 shows the interior of the switch case. This part of the mechanism controls the interruption of the battery current. The current is supplied to the interruptor through a polarity reverser, which reverses the direction of the current each time the switch button is turned. This equalizes the wear on the contact points.

Attention is again called to the distributor blade shown in Fig. 82, which is used for both systems. Because of the shape of this blade, there is a continuous flow of sparks after the explosive spark has been delivered to one cylinder until the forward edge of the distributor blade is within range of the distributing point of the next terminal. By this action the first spark delivered to the cylinder is an efficient one, and the follow up continues at intervals of approximately one-thousandth of a second. These sparks are all perfectly synchronous.

The operation of the high frequency system does not differ in function action from the single spark system explained on the foregoing page. Either system may be had singly, or in duplex formation. Consequently either the single or the double system may be encountered. When the duplex system is used the driver has his choice and can use either the high frequency or single spark system, by turning the rubber roll switch on the distributor to the system indicated.

This follow-up feature has been found particularly advantageous for starting in cold weather, or where a poor grade of gasoline is encountered, and in case of a poor carburetor adjustment or foul spark plugs. The high frequency system also has the unique feature of keeping the spark plugs clean without disintegrating the electroids, as is often the case with the high tension magneto.

Fig. 83 shows the Duplex switch. Ordinarily a storage battery is used for one source of current, and a set of dry cells for the other. This is so arranged that either source of current can be used with either the single spark system or the high frequency system at will. One source of current only can be used if so desired, that is, the storage battery only or the dry cells alone. Where the source of current is dry cells only, the single spark system is used as it is more economical in current consumption. All of the switch contacts are of the pressure plunger type, thereby eliminating the uncertainty of brush contacts. Each switch is provided with a lock operating through the hub of the lever. When the switch is locked in the off position it is impossible to remove the cover without breaking it as the cover of the switch locks to the back.

Ratchet buttons select which one of the systems is to be used, by a movement of 45°. This button operates only in a clock-wise direction.

Fig. 84 shows a wiring diagram of the Philbrin system. The wire connections come to the contact maker directly from the switch, instead of from the coil. This provides for control of the current to the contact maker in such a manner that if a short circuit occurs in either of the systems, by turning a button it is entirely cut off and the other system put into operation.

Tungsten contact points are used on the single spark system as they are not effected by the use of light oil. The contact points for the high frequency system are platinum-iridium. They are mounted inside of the switch case and need little or no attention. The contacts, due to the reversed polarity, have an extremely long life and can be used without attention until they are worn down to the base metal. The duel type of system, however, may be purchased in separate units, and an owner may choose either the high frequency system or the single spark system separately if so desired.

This type of ignition system is manufactured for four, six, eight, and twelve cylindered cars.