Abstract:
An apparatus that can be used to jump-start a car that has a weak battery. It includes a battery booster pack or a battery booster cable that is polarity sensitive and can detect proper and improper connections before providing path for electric current. This apparatus eliminates the danger of reverse connections, shorts, fires, spark firing and battery explosion. The apparatus requires no separate switching mechanism to turn power on or power off. It also does not require the imperfect human judgment of any indication device to determine correct or incorrect connection. The clamps detect for the correct polarity and automatically control the power. Power turns on once a good connection has been made. If user makes a wrong connection, there will be no power but its warning signal will go off. Once a clamp is dislodged from the battery terminal, it automatically turns power off without the need to deactivate a switch. This apparatus also provides safe and automatic power on/off control for the booster cable and booster pack.

Description:
BACKGROUND OF THE INVENTION 
     This invention pertains to a portable device that provides additional battery power for jump-starting stranded vehicles whose internal battery is discharged. 
     There are two types of existing products of similar function in the market: 
     A Booster Cable is a pair of parallel cables. Each end of the cable is attached to one pair of alligator clamps. The clamps are clamped on to the battery terminals so that electric current flows from a boosting battery to the discharged battery. This provides power to start the stranded vehicle. 
     A Booster Pack is a pair of cable connected at one end to the built-in battery of a portable box while the other end connected to a pair of alligator clamps. When the clamps are connected to a discharged battery, current flows from the built-in booster battery of the booster pack to the discharged battery of the stranded vehicle. 
     For booster cable sets and booster packs, it is important that user will makes the correct polarity connection between the clamps and the batteries. If the connection is reversed, firing sparks will discharge at the contact points and may cause damage to property or to people. 
     Traditionally, many inventors attempted to reduce or to eliminate the risk of reverse connections associated to the use of booster cable sets. In U.S. Pat. No. 4,366,430, Wright taught an art using a manual switch and a voltage detector in order to determine whether a connection was safely made. Further, in U.S. Pat. No. 4,420,212, Wright taught another art of using light emitting diodes (“LED”) for indication of polarity of connection. Later, McGowan, in U.S. Pat. No. 5,796,255, disclosed another art of using LED art and voltage detection method to indicate and detect correct connection in using booster cable sets. These methods can detect an improper connection. Upon viewing the good connection, the user will press a switch to complete the electric path between the booster battery and the discharged battery. 
     The inventions require user to make judgment based on viewing the LED indication and then manually activate the switch to complete an electric path between the two batteries. Also, after the booster cable successfully jumped starting the stranded vehicle, the inventions require user to activate switch again to terminate the electric path. If a careless user forgets to press the switch after jump starting a stranded vehicle, the dislodged clamps may discharge firing sparks. The same peril exists when a second connection is made with reverse polarity. 
     Other inventors have attempted to reduce or to eliminate the spark risk when using booster packs. In U.S. Pat. No. 5,589,282, Roxon disclosed an invention providing a holster to house the permanently charged clamp of the booster pack. In this invention, the holster is permanently attached to the main portable enclosure body of the booster pack unit. In U.S. Pat. No. 5,183,407, Srol invented the use of an insulated cap to protect the charged clamp of the booster pack unit. 
     In these booster pack inventions, once the user dislodges the clamps from either the holster or the cap, the peril of an improper connection remains. 
     This invention solves all of the above problems of reverse connections, shorts, spark firing and battery explosion. The solution is provided below in the detailed description. 
     BRIEF SUMMARY OF THE INVENTION 
     This present invention is a booster pack and a booster cable that eliminates the danger of reverse connections, shorts, fires, spark firing and battery explosion. The invention requires no separate switching mechanism to turn power on or power off. It also does not require the imperfect human judgment of any indication device to determine correct or incorrect connection. 
     The clamps detect for the correct polarity and automatically control the power. Power turns on once a good connection has been made. If user makes a wrong connection, there will be no power but its warning signal will go off. Once a clamp is dislodged from the battery terminal, it automatically turns power off without the need to deactivate a switch. This invention also provides safe and automatic power on/off control for the booster cable and booster pack. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A detailed description of the embodiments of the invention will be made with reference to the accompanying drawings, wherein like numerals designate corresponding parts in figures. 
     FIG. 1 is a Diagram of a Clamp 
     FIG. 2 a  is a Diagram of the Top View of the Solenoid Assembly in Closed State 
     FIG. 2 b  is a Diagram of the Left View of the Solenoid Assembly in Closed State 
     FIG. 2 c  is a Diagram of the Front View of the Solenoid Assembly in Closed State 
     FIG. 2 d  is a Diagram of the Right View of the Solenoid Assembly in Closed State 
     FIG. 3 a  is a Diagram of the Top View of the Solenoid Assembly in Open State 
     FIG. 3 b  is a Diagram of the Left View of the Solenoid Assembly in Open State 
     FIG. 3 c  is a Diagram of the Front View of the Solenoid Assembly in Open State 
     FIG. 3 d  is a Diagram of the Right View of the Solenoid Assembly in Open State 
     FIG. 4 is a Circuit Diagram of the Best Mode of the Polarity Sensitive Booster Pack 
     FIG. 5 is a Circuit Diagram of the Best Mode of the Polarity Sensitive Booster Cable 
     FIG. 6 a  is a Control Block Diagram of the Best Mode of the Booster Cable in Short Circuit State 
     FIG. 6 b  is a Control Block Diagram of the Best Mode of the Booster Cable in the Normal Working State 
     FIG. 6 c  Control Block Diagram of the Best Mode of the Booster Cable in the Natural State 
     FIG. 7 a  is a Diagram of the Booster Pack in the Normal Working State 
     FIG. 7 b  is a Diagram of the Booster Pack in the Reverse Polarity State 
     FIG. 7 c  is a Diagram of the Booster Pack in the Short Circuit State 
     FIG. 8 a  is a Diagram of the Internal Construction of the Control Box for the Booster Cable where the Solenoid is in Open State 
     FIG. 8 b  is a Diagram of the Internal Construction of the Control Box for the Booster Cable where the Solenoid is in Closed State 
     FIG. 8 c  is a Drawing of the Top View of the External Construction of the Control Box for the Booster Cable 
     FIG. 8 d  is a Drawing of the Left View of the External Construction of the Control Box for the Booster Cable 
     FIG. 8 e  is a Drawing of the Right View of the External Construction of the Control Box for the Booster Cable 
     FIG. 8 f  is a Drawing of the Front View of the External Construction of the Control Box for the Booster Cable 
     FIG. 9 a  is a Drawing of the Back View of the External Construction of the Housing for the Battery Booster Pack 
     FIG. 9 b  is a Drawing of the Side View of the External Construction of the Housing for the Battery Booster Pack 
     FIG. 9 c  is a Drawing of the Front View of the External Construction of the Housing for the Battery Booster Pack 
    
    
     DETAILED DESCRIPTION 
     I. Polarity Sensitive Booster Cable 
     A. Working Theory of the Polarity Sensitive Booster Cable 
     Let&#39;s first look at the fundamental theory behind the special booster cable. Like a regular booster cable, the special booster cable in this invention has four sets of alligator clamps and each Clamp A 10 , as seen in FIG. 1, is connected to a power cable A 5 . These power cables are connected to a Control Box H 1 , which provides space to house a Solenoid Assembly K- 1 , as seen in FIG. 2 a  and a Control Circuit, as seen in FIGS. 5 and 6 a . The Control Circuit receives and compares polarity signals from the signal wires connected to jaws at the clamps. Through the connected jaws and signal wires, the circuit receives signals from contacts with battery terminals. If the connection polarity is good, the control circuit will charge the solenoid assembly K- 1 . The charged Solenoid Assembly will provide a path for current power to flow through. If the polarity of connections is not good, the Control Circuit will not charge the Solenoid Assembly and no path is provided for power current. There is no spark generated at the jaws. Further, the circuit can turn on the Buzzer Signal BZ 1  to alert user that a wrong connection has been made. 
     B. Details of the Polarity Sensitive Clamps 
     Let&#39;s now look at the details of the clamps A 10  as seen in FIG.  1 . The clamps look similar to any traditional clamp. This polarity sensitive clamp is comprised of two handles, A 1  and A 2 . The heads of the two handles are each attached to one Jaw Fixture A 7  and A 8 . The Jaw Fixtures A 7  and A 8  can be attached to the two handles A 1  and A 2  by insulated rivets, forming opposing jaws. Jaw A 7  is connected to the power cable A 5  and jaw A 8  is connected to a signal wire A 6 . For convenience sake, Jaw A 7  is referred to as the “Power Jaw”, and jaw A 8  is referred as the “Sense Jaw” or “Signal Jaw”. A plastic cap placed between the Sense Jaw A 8  and the handle A 2  for insulation, while the opening of the cap exposes the jaw teeth for electric contact. The signal wire A 6  is embedded inside power cable A 5  but is insulated therefrom. The opposite end of power cable A 5  is connected to a conductive hexagon post of a solenoid assembly further discussed below. The opposite end of signal wire A 6  is connected to the electronic control circuit (see below for details). Handles A 1  and A 2  are held together by rivet pin A 3  and spring A 4 . In the preferred embodiment, a rivet pin should be used as the inventor believes this is the best mode, though other means are possible. When handles A 1  and A 2  are squeezed, the jaw mouth of Power Jaw A 7  and Sense Jaw A 8  will open. There will be no contact between each other. As a result, even if power cable A 5  carries electric current, signal wire A 6  will not receive any volt signals from power cable A 5 . 
     C. Detailed Structure of the Solenoid Assembly 
     Let&#39;s now look at the details of the solenoid assembly, K- 1  as seen in FIG. 2. A moving plunger B 1  is placed inside the solenoid coil. The plunger B 1  has the tail end exposed outside the solenoid housing. The tail of plunger B 1  is attached to a flat shape conductive contact plate B 2 . The inventor believes that the flat shape of the conductive contact plate is the best mode, but also believes that other shapes of plates could also be substantially adequate. A spring, B 3 , sits between the conductive contact plate B 2  and the solenoid coil housing and is inserted onto the plunger B 1 . 
     A pair of hexagon shape conductive posts, B 4  and B 5 , which are insulated at the base, are sitting perpendicular to the plunger B 1  and the spring B 3 , and between the contact plate B 2  and the solenoid housing. One post B 4  is connected to the power cable A 5 . The opposite post, B 5  is connected to another power cable, which if used in a battery booster pack, is connected to a built-in battery, or, if used in a booster cable, is connected to the opposite end of the power cable A 5 . The two conductive posts B 4  and B 5  are aligned with their flat face parallel to the contact plate B 2 . This position provides for a larger contact surface area between the posts and the contact plate. 
     When the solenoid coil is charged, as in FIG. 2, it generates a magnetic force and induces the moving plunger B 1  to move toward the inner end of the solenoid housing. The motion also pulls the contact plate B 2  travelling in the same direction but was blocked by the two conductive posts B 4  and B 5 . As a result, the magnetic force presses the contact plate B 2  on the surface of B 4  and B 5 , forming a path for electric current between these two posts. Through the two posts, power current can flow through this booster cable and offer jump-starting power to a discharged battery. 
     If the solenoid coil is not charged, as in FIG. 3, the spring B 3  pushes the contact plate B 2  away from the conductive posts, B 4  and B 5 . There will be no path between the two posts and no power current will be flow through the posts. Since there are power cables connecting the battery terminals of opposite battery sources, the absence of path switches off the booster cable and there will be no spark at the jaws. 
     D. Control Circuit of the Booster Cable System 
     Now let&#39;s look at the detail structure of the control circuits of the booster cable, as seen in FIG.  5 . The circuit controls two pairs of cables, each connected to one polarity sensitive clamp as explained above. Each pair is connected on one side of the control box H 1 . One pair of the cable is shorter in length. For purpose of convenience, this shorter cable is referred hereafter as the “A” side. The opposite pair of cable, the longer pair, is referred hereafter as the “B” side. 
     1. Good Connection Case 
     Assume that the user makes the first connection with the A side to a battery and further assume that it is a good connection. The positive clamp (also called a clip) is connected to the positive terminal and its negative clamp (also called a clip) is connected to the negative terminal. Current passes through diode D 3  and powers the entire circuit group. It returns through diode D 2  from the common path back to the battery source. When the user makes the second connection at the B side to a second battery source, voltage is applied at the Signal Jaw A 7  of the positive clamp. Its current energizes resistor R 1 , optic coupler OC 2  and returns to the battery source through the contact at the Signal Jaw at the negative clamp. Current lights up the internal light emitting diode within optic coupler OC 2  and turns on the transistor section. Through the path provided by the transistor, current routes through resistor R 4  and turns on the transistor Q 4 . At the same time the current branches through diode D 6 , resistor R 9  and transistor Q 9 . Transistor Q 9  is also turned on. 
     When transistors Q 4  and Q 9  are energized, the circuit group is in a stand-by condition. Yet, the solenoid K 1  remains open and no path is provided for current flow between the two batteries. 
     If the second connection at the B side is correctly made, with the positive clamp on the positive terminal and the negative clamp to the negative terminal, voltage is applied at the Signal Jaw A 8  in the positive clamp. Its current energizes resistor R 13 , optic coupler OC 3  and returns to the battery source through the contact at the Signal Jaw A 8  of the negative clamp. Current lights up the internal light emitting diode within optic coupler OC 3  and turns on the transistor section. Current then flows through resistor R 7  and the base prong of transistor Q 3 . 
     Since transistor Q 4  is on, a path is therefore established so that transistor Q 3  is energized. Current flows through resistor R 2  and R 3 . The voltage potential across resistor R 2  will bias the base prong of the transistor Q 1 . Transistor Q 1  will be turned on. Current will flow through the collector prong of transistor Q 1 , resistor R 5  and the base prong of transistor Q 2 . Transistor Q 2  will be turned on. 
     Thus, current will flow through solenoid K 1  and will energize its coil. Magnetic field around the solenoid induces motion of the plunger B 1 , shown in FIG.  2 . The plunger forms a path between the two hexagonal posts. Voltage is applied across diode D 11  in FIG. 5, resistor R 11 , transistor Q 7 , a light emitting diode LED 1  and resistor R 17 . Transistor Q 7  is fully turned on and current will turn on the light emitting diode LED 1 , advising user that the connections are good. Current will flow from a good battery to a low battery, which is usually in a stranded car. 
     After jump starting of the stranded car has been accomplished, the user disconnects one clamp on side A. Either one of the two Signal Jaws on side A is disconnected from the battery terminal which interrupts the path in optic coupler OC 2 . Or alternatively if the user disconnects one clamp on side B, one of the two Signal Jaws on side B is disconnected from the discharged battery terminal which interrupts the completed path in optic coupler OC 3 . 
     The above disconnection either shuts down the internal light emitting diode within optic coupler OC 2  or OC 3 . As the internal light emitting diode is off, the transistor section will be turned off, removing the current on transistor Q 3  or Q 4 . Since these transistors are connected in series, turning either one off will interrupt the entire flow path. Transistors Q 3  and Q 4  will be turned off, which in turn shut down transistors Q 1  and Q 2 . Consequently, current to energize the coil winding of solenoid K 1  is disconnected. The magnetic induction is terminated. The spring pushes the contact plate away from the two posts, and terminates the current path between the two batteries. Diode D 5  is a safety precaution to protect transistor Q 2  from a possible high voltage spike. 
     2. Reverse Connection Case 
     Let&#39;s now assume that the user makes a reverse connection. The positive clamp of side A is connected to the negative terminal of a battery and the negative clamp connected to the positive terminal of the same battery. Once connection is established, voltage is applied across the Signal Jaw in the positive clamp. Its current energizes resistor R 1 , optic coupler OC 1  and returns to the battery source through the contact at the Signal Jaw of the negative clamp. Current lights up the internal light emitting diode within optic coupler OC 1  and turns on the transistor section. Current then flows through resistor R 8  and energizes transistor Q 6 . Current also branches through diode D 8 , resistor R 12  and the transistor Q 8 . Therefore transistor Q 8  is ready to be turned on and the circuit group is at standby condition. 
     Assuming at this point the User connects the positive clamp of side B to the positive terminal of another battery, and the negative clamp to the negative terminal of the same battery. Voltage is applied across the Signal Jaw in the positive clamp. Its current energizes resistor R 13 , optic coupler OC 3  and returns to the battery source through the Signal Jaw of the negative clamp. Current will light up the internal light emitting diode within optic coupler OC 3  and turn on the transistor section. Current continues to flow through resistor R 7  to the base prong of transistor Q 3 . Since transistor Q 4  and Q 3  are connected in series and Q 4  at this point is at off status, Q 3  will remain at off status. Therefore, although transistor Q 6  is on, transistor Q 5  is at off status and no path is provided for current flow. Consequently, there is no power to drive transistor Q 1  and it will keep transistor Q 2  in off status. 
     With the transistors in off status, there is no current to energize the solenoid K 1 . The current path remains open and no current flow between the two batteries. Thus, the reverse connection does not cause any spark or any explosion. 
     Yet, when the current is flowed through resistor R 7  to the base of transistor Q 3 , it also branches through diode D 7 , resistor R 9  and the transistor Q 9 . Transistor Q 8  will be biased on through resistor R 12  via the collector-emitter junction of transistor Q 9 . As both transistors Q 8  and Q 9  are on, the base prong of the transistor Q 10  will be pulled low through resistors R 14  and R 15 . Transistor Q 10  will be turned on. Current flows through to turn on the buzzer BZ 1  and the light emitting diode LED 2  for alarm purpose, advising user that a reverse connection has been made. 
     3. Double Reverse Connection Case 
     Let&#39;s now assume that the first connection at “A” side was made with the positive clamp connected to the negative terminal of the first battery source, and also the negative clamp connected to the positive terminal of the same battery. As a connection is established, voltage is applied through the Signal Jaw in the positive clamp, through resistor R 1 , optic coupler OC 1  and the Signal Jaw in the negative clamp. Current energizes internal light emitting diode within optic coupler OC 1 , so the transistor section will be turned on. A path is formed so that current is flowed through resistor R 8  to turn on transistor Q 6 . At the same time the current branches through diode D 8 , resistor R 12  and the transistor Q 8 . Therefore transistor Q 8  is ready to be turned on. 
     If at this time the positive clamp on the “B” side is connected to the negative terminal of a second battery source and the negative clamp to the positive terminal of the same battery. Voltage is applied across the contact formed by the Signal Jaw in the positive clamp, resistor R 13 , optic coupler OC 4  and the contact formed by the Signal Jaw in the negative clamp. Current will flow through internal light emitting diode within optic coupler OC 4  and light up it, the transistor section will be turned on. Current flows through resistor R 6  to the base of transistor Q 5 . As transistor Q 6  has been in “on” position, so the in series connected transistor Q 5  is also turned on. A path is formed. Base of the transistor Q 1  is pulled low through resistors R 2  and R 3 . The voltage potential across resistor R 2  will bias on the base of the transistor Q 1 . Therefore transistor Q 1  will be turned on. Current will flow through the collector of transistor Q 1 , resistor R 5  and the base of transistor Q 2 . In turn, transistor Q 2  is on and current will charge the solenoid K 1 . Its magnetic field will induce the contact plate to form a path of current between the two batteries. Further, voltage is applied across diode D 11 , resistor R 11 , transistor Q 7 , light emitting diode LED 1  and resistor R 17 . Transistor Q 7  is fully on and current flow turns on the light emitting diode LED 1 . It advises user that a correct connection has been made, despite both connections were made reversed. 
     II. Battery Booster Pack 
     A. Working Theory of the Battery Booster Pack 
     Now let&#39;s look at the working theory of the battery booster pack as seen in FIGS. 9 a-c . The booster pack is a portable device with a plastic housing H 2 . It provides for space to house a built-in battery, a solenoid assembly and a control circuit. It also has light emitting diodes to display the voltage level of the built-in battery. A built-in charger is housed in the charger compartment. User may insert an extension for recharge purpose. A separate light emitting diode will be turned on showing the built-in battery is being charged, once voltage is applied through the charger. 
     A female cigarette light receptacle is provided for  12  volt power source  91 . The receptacle is connected to the built-in battery as a power bank. 
     A bi-color light emitting diodes, LED 1  (green in color) and LED 2  (red in color) provides for advice to user on the status of connection between the booster pack and the outside battery. A green light indicates a good connection. A red light indicates a wrong connection. When the red light is turned on due to a wrong connection, the built-in buzzer will also go off to warn the user. 
     This battery booster pack has three power cables. Only two are exposed to the outside of the plastic housing H 2 . The first exposed cable connects between one conductive post of the solenoid assembly (see above for details) and the red color coded clamp, referred as the “Positive Clamp”. The second exposed cable connects between the negative terminal of the built-in battery and the black color coded clamp, referred as the “Negative Clamp”. The third cable, hidden inside the plastic housing H 2 , connects between the positive terminal of the built-in battery and the opposite conductive post of the solenoid assembly (see above for details). 
     The said Positive Clamp and the Negative Clamp has same structure as clamps used in the above booster cable systems. Each is provided for a Power Jaw A 7  and a Sense Jaw A 8 . Through the Sense Jaws, the control circuit determines whether connections to an outside battery is good. If it determines that a good connection has been made, it will charge the solenoid assembly and engage the path for power current at the contact plate. If the connection is not good, it will not engage the path but will turn on the alarm, with a red light LED 2  and buzzer BZ 1 . 
     B. Booster Pack Control Circuit Details 
     Let&#39;s assume the user makes a good connection. One places the Positive Clamp on the positive terminal of an outside battery on a stranded vehicle, and one also connects the Negative Clamp to the negative terminal of the same discharged battery. 
     As this point, voltage is applied across the contact formed by the signal jaw in the positive clip, resistors R 10 , R 9  and R 7 , and the contact formed by the signal jaw in the negative clip. Voltage potential across resistor R 7  will bias on the base-emitter junction of transistor Q 4 . A path is formed. The base voltage potential of transistor Q 2  is pulled down by resistors R 3  and R 4 . Therefore transistor Q 4  is turned on. The collector current will flow to the base terminal of transistor Q 3  through resistor R 5 . Transistor Q 3  is also be turned on. 
     Current flows through diode D 1  to the coil winding of the solenoid K 1  and energizes it. Once the solenoid is charged, induction force will engage the contact plate with the two metal hexagon posts to form a current path between the two. Power current flows through from the positive terminal of built-in battery, through the two conductive posts, to the positive terminal of the outside discharged battery, returns through the negative terminal of the discharged battery back, through the Negative Clamp to the built-in battery. 
     C. LED Operation 
     When the clamps are connected to the terminals of the discharged outside battery properly, voltage is applied across the contact formed by the signal jaw in the positive clip, resistors R 10 , diode D 3  and resistor R 8 , and the base-emitter junction of transistor Q 5 , and the contact formed by the signal jaw in the negative clip. Voltage potential will bias on the transistor Q 5  and will turn it on. A path can be formed where the base voltage potential of the transistor Q 1  is pulled down by the resistors R 2  and R 6 . Thus, transistor Q 1  will turn on and the collector current will flow to the light emitting diode LED 1  through the resistor R 1 . The green color light emitting diode LED 1  will be on to indicate the status of ready to engage. 
     D. Disconnection 
     When the stranded vehicle is successfully jump-started, user will disconnect any one of the two clamps. The disconnection discontinues the connection formed by the signal jaw of the dislodged clamp, either the Positive Clamp or the Negative Clamp. Consequently, the control path from the contact formed by the signal jaw in the positive clip, resistors R 10 , R 9  and R 7 , and the contact formed by the signal jaw in the negative clip is interrupted. Transistor Q 4  will lose its bias voltage and will be turned off, removing the current driven on the transistor Q 2 . 
     As transistor Q 2  is turned off, transistor Q 3  is also turned off. Thus, there is no current to charge solenoid K 1 . The induction force is terminated and no magnetic induction is available to hold the contact plate to the two posts. The current path between the positive terminal of the built-in battery to the discharged battery is gone. The battery booster pack is switched off automatically simply by dislodging any clamps after jump starting a stranded vehicle. 
     E. Reverse Connection Case 
     Now let&#39;s assume the user makes a wrong connection. One lodges the Positive Clamp to the negative terminal of an outside discharged battery, and also the Negative Clamp to the positive terminal of the outside battery. 
     Voltage is applied across the contact formed by the signal jaw in the positive clip, resistor R 10 , optic coupler OC 1  and the contact formed by the signal jaw in the negative clip. Current flows through internal light emitting diode within optic coupler OC 1  and light it up, so the transistor section will be turned on. Current flow powers up buzzer BZ 1  and goes through resistor R 11  to turn on light emitting diode LED 2  in red color for alarm purpose. 
     As the base-emitter junction of transistor Q 4  is reversed biased, it remains in off position. The path can not be formed through resistors R 3  and R 4 . Transistor Q 2  has no biasing source and also be in the off state. The transistor Q 3  is also in the off state. The solenoid K 1  is not energized. Contact plate remains away from the two conductive posts and no path is provided for current between the two batteries. 
     Although a reverse connection has been made, there is no power on either clamp so that there is no spark to cause any dangerous explosion. As the base-emitter junction of transistor Q 5  is reversed biased, it is off. The path can not be formed through resistors R 2  and R 6 . Transistor Q 1  has no biasing source to drive on so that it would be in off state; No current will flow to the light emitting diode LED 1 , so it is not lit up.