Patent Publication Number: US-6659783-B2

Title: Electrical connector including variable resistance to reduce arcing

Description:
CROSS REFERENCE TO PRIOR CO-PENDING PATENT APPLICATIONS 
     This application claims the benefit of Provisional Patent Application Serial No. 60/309,424 filed Aug. 1, 2001 and of Provisional Patent Application Serial No. 60/324,111 filed Sep. 21, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electrical connector including means for preventing or suppressing an arc when power contacts are disconnected or separated while they carry substantial power or electrical current. This invention also relates to an electrical connector that preferentially uses a positive temperature coefficient resistor shunted between contacts that are disconnected sequentially so that voltage and current will be below a threshold at which arcing might occur, when each contact is separated from a mating contact. 
     2. Description of the Prior Art 
     Contacts carrying significant amounts of power will arc when disconnected. The amount of arc damage experienced by the contacts depends on their physical structure, the load current, the supply voltage, the speed of separation, the characteristics of the load (resistive, capacitive, inductive) as well as other factors. 
     Future automotive systems are expected to utilize 42 volts in order to reduce the load currents and the associated wiring losses. This increased voltage could cause significant arc damage to occur to the present connectors designed for 12-volt operation. To avoid the possible liabilities associated with catastrophic connector failure, automotive manufacturers are requesting a new connector design that can be hot-swapped some significant number of times. Ten cycles is considered to be a minimum requirement. 
     To disconnect 42-volt power without significant damage requires interrupting about 1500-watts for many loads and as much as 15 KW for the main battery circuit. Present day modules used in automotive applications can consume more than 500 watts. Power supplies must deliver one or more kilowatts of energy. Conventional solutions require either that the current be shut off before the contacts are separated or unmated or employ a sacrificial contact portion. The cost, space, reliability, safety, performance and complexity of these conventional solutions make them unsuitable for many applications, including automotive electrical systems. 
     There are many things known in the power utility profession that will quickly extinguish an arc and there are many things known in the relay industry that will minimize arc damage to connectors and contacts. These can be found in literature, such as  Gaseous Conductors  by James D. Cobine and the  Ney Contact Manual  by Kenneth E. Pitney. Most of these methods are not practical in smaller and separable electrical connectors such as those used in automobiles, computers and appliances. None of the methods provided in the literature will eliminate arcing. Conventional contacts will be destroyed when rated currents are interrupted often enough and slowly enough, even though these conventional contacts may rated for current interruption. There is a finite life for existing connectors since arcing will occur and cause damage each time the connector is disconnected under load. 
     U.S. Pat. No. 4,079,440 disclosed the use of an impedance element between a long and a short contact to avoid an arc and consequent damage to the short contact. The impedance element can be a fixed capacitance and an inductance is included to limit inrush current. It is suggested that a resistance or a resistance in series with a capacitor could also be used as an impedance element. U.S. Pat. No. 4,681,549 discloses the use of a current limiting resistor between long and short pads on a printed circuit board. The use of a constant impedance, capacitance or resistance in this manner will tend to limit or suppress an arc in only limited circumstances. Fixed capacitors and resistors are only suitable for a relatively small range of currents and voltages. An electrical connector will typically be used for a much larger range of currents and voltages than can be practically accommodated by a fixed capacitor or a fixed resistance, which may prevent or suppress arcing for only a portion of the applications in which an electrical connector will be used. 
     Positive Temperature Coefficient Resistance (PTC) Devices, resistors or switches have been used, or suggested for use, in circuit breakers that are used to break fault currents, specifically defined and excessive overcurrents, for which these circuit breakers are rated. On the other hand, electrical connectors are expected to carry a wide range of currents during actual use. Even though an electrical connector may be rated to carry a specific current, in actual practice, an electrical connector will carry currents over a large range due to variations in the load. The cost, size and weight of an electrical connector will generally increase with increasing current rating, so the lowest rated connector suitable for use in a specific application will normally be used. Because multiple loads with different current needs pass through a single connector, as well as for economic, inventory and connector product line consistency, it is not uncommon to minimize the number of different connectors utilized in a specific product. The net result, is that a specific connector will carry anywhere from its rated current, or even an overcurrent for safety and life testing, to some significantly lower current. If that connector is to be disconnected while carrying a current, or hot swapped, without arcing, arc prevention must be effective for a large range of currents, starting from the arc threshold current to the rated current for that connector. In other words, unlike circuit breakers, hot swapped connectors must be protected from arcing over a wide range of currents. Therefore use of a PTC resistor in the same manner as it is used in a circuit breaker will not be suitable for use in an electrical connector. The trip time varies for a PTC device in which resistance is dependent upon the temperature of the device, and the temperature is dependant upon current because of I 2 R heating. Thus the trip time for a PTC device used in an electrical connector will vary because of the wide range of currents that will be carried by a particular electrical connector. 
     When PTC resistance devices are used in switches, relays, fuses and circuit breakers, both halves of electrical contacts remain within the same physical device. The contacts separate from each other, but only by a well defined and fixed distance, and the separated contacts are still part of the device package. The essential function of electrical connectors is to totally separate the two contact halves. No physical connection remains between the two halves, and all physical ties are broken between two mating connector contacts. In order to protect separating electrical contacts that are carrying arc-producing power, the PTC device must be connected across the contact pair until the current is sufficiently reduced to prevent arcing. Thus, the problem is that a physical electrical connection to both halves of the separating electrical contact must be maintained in a conventional use of a PTC device yet, in a connector, all physical connections must be broken. 
     In switches, relays, fuses and circuit breakers, where prior art PTC devices are used; the distance of contact separation and the rate of separation are controlled. In these prior art devices, the contact separation needs to only be enough to hold off the rated voltage. The rate of separation can be made as fast as possible to shorten the time in which arcing could occur, therefore minimizing any associated damage. Electrical connectors must be completely separated. Electrical connectors are also manually separated, and the rate of separation varies widely for existing electrical connectors. Even for a specific manually separated electrical connector design, the rate of separation will vary significantly each time two electrical connectors are manually unmated. 
     SUMMARY OF THE INVENTION 
     To overcome these problems, the instant invention preferably employs a positive temperature coefficient (PTC) resistor in an electrical connector in series with an auxiliary electrical contact portion or contact terminal, the combination of which is in parallel with a main electrical contact portion or contact terminal, which disconnects first. This arrangement of components parts will prevent arcing when two electrical connectors are unmated while carrying current. Both the main and the auxiliary contacts are matable with a terminal or terminals in a mating electrical connector. In the preferred embodiments, the main and auxiliary contacts are male terminals or blades that mate with a female or receptacle terminal in the mating electrical connector. However, the PTC resistive member could also be employed with the female terminals. The PTC resistive member should, however, only be employed with the terminals in one half of a mating pair of electrical connectors. The main or auxiliary contact portions or terminals in one of the two connectors must incorporate the PTC member. When a conventional discrete PTC member, such as a commercially available POLYSWITCH® device, is used, the main and auxiliary contact portions or terminals in the other of the two mating connectors must be connected together directly, with no discrete PTC device between them. However, in other applications the PTC means may be located in both connectors. 
     A discrete PTC resistive member can be employed into the main and auxiliary contact terminals so that the PTC device can form an integrated unit. One means for forming such an integrated unit would be to mold a PTC conductive polymer between the main and auxiliary contact terminals. The PTC conductive polymer could also be overmolded around portions of the main and auxiliary contact terminals, with the PTC conductive polymer being molded between the main and auxiliary contact terminals. Insert molding techniques could be used to position the PTC conductive polymer between, the main and auxiliary contact terminals. The PTC conductive polymer could also be a discrete component that is molded as a shape that would conform to parts of the main and auxiliary contact terminals and this discrete component could be bonded between the main and auxiliary contact terminals using solder, a conductive adhesive or some other conductive bonding agent. 
     The main contact should unmate before the auxiliary contact, and in the representative embodiments depicted herein, the auxiliary contact is longer than the main contact. In the preferred embodiment, the PTC member comprises a conductive polymer member in which conductive particles are contained within a polymer matrix. Normally the conductive particles form a conductive path that have a resistance that is larger than the resistance of the main terminal so that under normal mated operation, the main contact would carry substantially all of the current. However, as current increases in the PTC member, the polymer expands and the resistance increases. When current through the PTC member increases rapidly due to disconnection of the main contact terminal, the resistance will increase rapidly due to I 2 R heating of the polymer. To prevent arcing when the main contact is unmated, the disconnect time for the main contact must be less than the time for the resistance of the PTC member to increase too greatly. Most of the current through the main contact must be carried by the PTC member and the auxiliary contact until the main contact has moved to a position in which arcing is no longer possible. Before the auxiliary contact is disconnected from the mating terminal, the resistance in the PTC member must increase so that the current flow through the auxiliary contact will drop below the arcing threshold before the auxiliary contact is unmated. This time is called the trip time of this PTC resitive member. Since the trip time of the PTC member will depend on the initial current through the main contact, which can vary over a wide range, the trip time for a given electrical connector will therefore not be constant. To insure that the PTC member will trip, the electrical connector of this invention employs latches that cannot be activated, after the disconnection of the main contact, for a time interval that will be greater than the maximum trip time for the PTC member. However, these latches must also permit rapid movement between the two electrical connectors as the main contact moves through a portion of its path in which it is susceptible to arcing. Similarly, the auxiliary contact must move rapidly through an arc susceptible region as it is disconnected. The preferred embodiments of this invention therefore use multiple sets of latches that must be sequentially disengaged, and which provide a time delay between disconnection of a first set of latches and the disconnection of a second set of latches. This time delay should be longer than the maximum PTC trip time. This multiple latch configuration provides a versatile implementation of the invention. If, however, a specific electrical connector serves loads with a small difference between maximum and minimum current loads, a simpler latch mechanism can be utilized. The maximum achievable parting velocity and the added length of the auxiliary contact could in some cases provide adequate time for the PTC device to trip. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view of the stages that a representative electrical connector terminal, according to this invention, will pass while being unmated. 
     FIG. 2 is a view of mating contact terminals, according to a configuration used to demonstrate the characteristics of an electrical connector employing this invention. 
     FIGS. 3A-3C are representative plots showing the trip times for various currents of electrical connector terminals according to this invention. 
     FIG. 4 is a plot showing the variation of trip time to current. 
     FIG. 5 is a view of mated plug and header electrical connectors, according to the first embodiment of this invention, showing the position of a PTC device connected between two contact terminals. 
     FIG. 6 is a view of two unmated electrical connectors incorporating the first embodiment of this invention, and the terminals shown in FIG.  5 . 
     FIG. 7 is a view of the mated configuration of the two electrical connectors shown in FIG.  6 . 
     FIG. 8 is a view of the mating face of a plug connector incorporating receptacle contact terminals according to this invention. 
     FIG. 9 is a three dimensional view of the plug connector shown in FIG. 8 showing the sequential latches employed in the first embodiment of this invention. 
     FIG. 10 is a view of a header connector housing, matable with the plug connector shown in FIGS. 8 and 9. 
     FIG. 11 is a three dimensional view of the header shown in FIG. 10, showing two latching detents that are located at different positions along the mating axis of the electrical connector. 
     FIG. 12 is a three dimensional view of a receptacle contact terminal comprising a second embodiment of this invention. 
     FIG. 13 is a three dimensional view of a blade contact terminal comprising a second embodiment of this invention. 
     FIG. 14 is a view in which the mating terminals of FIGS. 12 and 13 are aligned prior to mating. 
     FIG. 15 is a side view of the mating terminals shown in FIG.  14 . 
     FIG. 16 is a top view of the mating terminals shown in FIGS. 14 and 15. 
     FIG. 17 is a view of the auxiliary contact terminal of the second embodiment of this invention. 
     FIG. 18 is a view of the main contact terminal of the second embodiment of this invention. 
     FIG. 19 is a view showing the manner in which the main and auxiliary contact terminals are position so that a PTC material can be overmolded. 
     FIG. 20 is a view of the matable plug and header connectors according to the second embodiment of this invention. 
     FIG. 21 is another view of the mating plug and header connectors of FIG.  20 . 
     FIG. 22 is a view showing the plug and header connectors of FIGS. 20 and 21 in a fully mated configuration. 
     FIG. 23 is a view of the mating face of the plug connector housing of the embodiment also shown in FIGS. 20-22. 
     FIG. 24 is a view of a lever that is used with the plug connector housing of FIG.  23 . 
     FIG. 25 is a view of the mating face of the header housing of the embodiment of FIGS. 20-23. 
     FIGS. 26-32 show the mating sequence of the two connectors of the second embodiment of this invention. 
     FIG. 26 is a side view of the two mating connectors of the second embodiment in a first mating position, showing the application of a force for initially mating the two electrical connectors. 
     FIG. 27 is a three dimensional view of the two mating connectors in the position also shown in FIG.  26 . 
     FIG. 28 is a detail view showing the position of the mating assist lever when the two connectors are in the position shown in FIGS. 26 and 27. 
     FIG. 29 is a side view of the two connectors of the second embodiment in a second position, showing application of a force to the mating assist lever. 
     FIG. 30 is a three dimensional view of the two connectors in the position of FIG.  29 . 
     FIG. 31 is a view of the two connectors of the second embodiment, showing the two connectors in a fully mated configuration and also showing the manner in which the lever can be unlocked. 
     FIG. 32 is a three dimensional view of the two connectors in the position also shown in FIG.  31 . 
     FIGS. 33-37 show the unmating sequence for the two connectors of the second embodiment. 
     FIG. 33 is a side view of the two connectors in an intermediate position in which the lever has been unlatched. This figure illustrates the position in which the lever can be used to disconnect the main contact. 
     FIG. 34 is a three dimensional view of the two connectors in the position also shown in FIG.  33 . 
     FIG. 35 shows the way in which latches are disengaged, after the lever has been rotated to its final position, so that the auxiliary contact terminal can be disengaged. The main contact is fully disengaged in this stage of the unmating cycle. 
     FIG. 36 is a three dimensional view of the two connector in the position also shown in FIG.  35 . 
     FIG. 37 shows the two connectors in a fully unmated position. 
     FIG. 38 is a photograph showing the damage that would occur when one prior art connector configuration is disconnected one time at 59 V, while carrying a current of 60 Amps. 
     FIG. 39 is a photograph showing a contact terminal configuration similar to that shown in FIG. 38 in which the instant invention has been employed to protect the mating sections of the terminals after they have been disconnected fifty times at 59 Volts, while carrying a current of 60 Amps. 
     FIG. 40 is a schematic representation of a means to protect an electrical system from the over-voltage effects of an inductive load. 
     FIG. 41 is a schematic representation of a second means to protect an electrical system from the over voltage effects of an inductive load. 
     FIGS. 42A-42D show and alternate embodiment in which a connector assembly employs a lever that provides rapid unidirectional movement through the contact disconnect zones and the time delay between them with a single lever. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A series of complex events lead to damaging arcs as contacts are separated while carrying substantial power. A simple description of the major events that occur in typical power contacts helps understand this phenomenon. First, as the contacts begin to separate, a point is reached where there is no longer enough metallic area to support the current flow. A very small molten bridge forms and breaks as the temperature and separation distance increase. Generally, this can occur at currents above 0.1 ampere and voltages greater than 9 volts. Enough current is needed to cause the melting and enough voltage is needed to sustain it and move to the next phase. As the molten micro-bridge boils and breaks, electrons are freed and current continues to flow by ionizing the intervening atmosphere. A true arc is the next result. This true arc consists of several sub-parts including the cathode spot, the cathode drop region, an extremely hot plasma channel, the anode drop region and the anode spot. The plasma channel is about 5000° C. and the anode and cathode spots reach about 2000° C. at 10-20 ampere currents. 
     If arcing is permitted to occur, mating contacts will be damaged. The degree of damage is controlled by many factors that determine the total arc energy. Primary ways to limit the arc energy are to minimize the current and voltage and by maximizing the separation velocity. There may be other means, but they do not lend themselves well to applications in which typical connector designs are utilized. For ordinary connectors, the only factor that can be controlled to a significant extent is the separation velocity. 
     By integrating a Positive Temperature Coefficient (PTC) resistance member into a two-piece contact, the voltage and current can be kept below the arcing threshold voltage and current when two connectors are unmated. This produces a contact that will not arc while interrupting significant energy as the connectors are disconnected. A PTC device, such as a discrete PTC resistor exemplified by a RHE 110 POLYSWITCH® device manufactured and sold by the Raychem division of Tyco Electronics Inc. may be employed. POLYSWITCH® is a registered trademark of Tyco Electronics Inc. The leads of the discrete device can be soldered to the respective main and auxiliary contacts. The leads on a discrete device could also be attached by contact springs or by crimps or by latching detents on the contacts. A conductive polymer, of the type exemplified by this discrete device can also be overmolded onto contact terminals to form a new component, or a PTC device can be integrated with the contact terminals to form an integrated component or unit. This approach may not eliminate the relatively benign spark that may occur when a high-energy circuit is connected. In the energy range of interest, this benign spark tends to do little damage to the contact base metal and to the shape of the contact. The general characteristics of POLYSWITCH® devices are discussed in U.S. Pat. No. 5,737,160 and the patents incorporated by reference therein. U.S. Pat. No. 5,737,160 and the other patent incorporated therein are in turn incorporated herein by reference for all purposes. The formulation of a conductive PTC device of the type used in a discrete POLYSWITCH® device is discussed in U.S. Pat. No. 6,104,587, which is incorporated herein by reference. This same formulation can also be used to form the conductive PTC polymer that can be molded into a shape compatible with the main and auxiliary contacts, or the PTC polymer can be overmolded or insert molded with the contact terminals as subsequently discussed with respect to the representative embodiments depicted herein. 
     FIG. 1 shows the concept for an arc-less power contact in accordance with the instant invention. Representative male and female, or blade and receptacle terminals, according to this invention, are shown in various stages of disconnection or unmating. There are three important components of the power contact illustrated in FIG.  1 . The main contact, or the main portion of the contact, carries the load current during normal operation. The main contact is shunted by a series connected, longer auxiliary contact or contact portion and by a positive temperature coefficient resistance or resistor, located between the main contact and the auxiliary contact. 
     FIG. 1 illustrates the four stages that occur during separation of the plug connector from the mating receptacle connector. In stage  0 , the contact is carrying a high current. The current is primarily flowing through the main contact or the main portion of the contact. Only a relatively small shunt current flows through the series connected positive temperature coefficient resistance or resistor (PTC) and the auxiliary portion of the contact. Stage  0  represents the normal operating configuration of a connector assembly. Relative movement of the two contacts in this position would result in the normal wiping action between two contact surfaces. 
     Stage  1  shows the configuration in which the main contact or main contact portion has been separated or disconnected from the mating contact in the other connector. The main blade is separated from the main receptacle through the main contact disconnect zone (MDZ), which occurs between Stage  0  and Stage  1 , in which the main blade contact is in the process of unmating from the corresponding female or receptacle contact. While the two contacts are in this main disconnect zone, the two contacts are not completely separated. Contact bounce may occur as the spring members flex and as irregular surfaces on the contact result in momentary separation and engagement. It is while the main contact and the receptacle contact are in this contact disconnect zone (MDZ) that arcing between the two connectors is most likely, since a relatively large existing current is being disconnected. For a conventional prior art connector, arcing could occur across a small gap in the MDZ, if the voltage and current are above an arcing threshold for the particular connector configuration. However, in the instant invention, the voltage and current across the opening gap are limited by the positive temperature coefficient (PTC) resistor or resistance and the auxiliary contact or contact portion. Duration of the MDZ should be less than the trip time for the PTC device so that the PTC device does not switch to an OFF or open condition before completion of the separation between the contacts. 
     When the mating contacts have moved to the position identified as Stage  1 , the main contact is physically separated from its mating contact so that arcing can no longer be initiated. Since there was only a small amount of current flowing through the PTC resistor during Stage  0 , the I 2 R heating remained low causing the resistance of the PTC resistor to be in a low state when the contacts reached the position identified as Stage  1 . Since the resistance is relatively low, current flows through the PTC resistor to the auxiliary contact and the PTC, which acts like a switch, can be said to be ON. While the auxiliary contact or auxiliary contact portion remains connected to the mating contact in the mating connector or to the same circuit in the mating connector, the current through the PTC resistor and the auxiliary contact will be greater than in Stage  1  and therefore I 2  R heating will increase. The resistance of the PTC resistor increases with increasing temperature. Stage  2  illustrates this configuration in which the longer auxiliary contact remains connected to the mating contact as physical unmating or relative movement between the connectors and contact terminals continues. Stage  2  illustrates a snapshot of one position of the contacts during the time after the main contact is separated and before disconnection of the auxiliary contact. It is during Stage  2  that the PTC resistor will open or, in other words, its resistance will significantly increase. Therefore, the PTC switch is now in the OFF position. 
     Prior to the time that the auxiliary contact separates from the mating contact, or from the circuit including the mating contact, the current flowing through the auxiliary contact will be below the arcing threshold. This is due to the increased resistance of the PTC during the time when relative movement of the two terminals or connectors occurs. This range of movement within the disconnect travel is called the PTC Opening Zone. When the auxiliary contact finally separates at Stage  3 , there is only a small amount of leakage current flowing through the connectors. At this point there will be insufficient electrical energy to support an arc between the auxiliary contact portions. Enough time should elapse while the terminals or connectors are in the PTC opening zone, so that the current is below the arcing threshold before the auxiliary contact is physically disconnected from the receptacle contact in the Auxiliary Disconnect Zone (ADZ). Stage  3  shows the mating contacts completely separated and disconnected with both the main contact and the auxiliary contact open. Since current is no longer flowing through the connectors, the PTC resistor will return to the RESET state of lower temperature and resistance. The contact assembly will then be in a state so that they will again function so that arcing will not occur when the connectors are unmated under load. 
     Preferably, this contact configuration is employed in a connector housing that provides velocity control to assure that the timing of the stages illustrated in FIG. 1 will be appropriate. The housing should also assure that unmating velocity is unidirectional. That is to say there should be no macro break-make-break action of the main contact as the connector separates. Nanosecond or micro discontinuities will occur, but these micro break-make-break actions will not interfere with the arc protection because the PTC resistor will be chosen to react much slower than these relatively high speed events. All four stages should be passed in a unidirectional and sequential manner. 
     The blade contact of FIG. 1 mates with the receptacle contact, which has flexible spring beams mating with the plug or blade contact. The plug or blade contact includes a main contact or main contact portion and an auxiliary contact or auxiliary contact portion. In this embodiment, the main contact and the auxiliary contact are two separate metal blades that each engage separate spring beams on the receptacle contact. In this representative configuration, the receptacle contact comprises a single piece metal member with separate spring beams engaging the main contact and the auxiliary contact respectively. The main contact and the mating receptacle contact are each printed circuit board style contacts with multiple leads extending from rear ends of each contact. The auxiliary contact or blade does not include means, such as the PCB leads, for connection to the external circuit independently of the main contact. The PTC resistor employed in this invention can comprise a molded member that can be bonded along at least one side to the central section of the main contact. A suitable conductive adhesive can be employed if necessary. The auxiliary contact is bonded to the PTC resistor along another side so that the PTC member is located physically and electrically between the main contact and the auxiliary contact. Stages  0 - 3  show the relative positions of the contacts as a connector in which these contacts are included are unmated. The PTC member employed herein preferably comprises a conductive polymer that can be molded to the desired shape. Conductive particulate fillers, such as carbon black, are dispersed in a nonconductive polymer to form a conductive path having a resistance that is dependent upon the temperature and state of the polymer. Devices employing a conductive polymer are well known and are available from Tyco Electronics. These POLYSWITCH® devices are employed in other applications. Barium-Titanate or semiconductor material exhibiting PTC behavior might also be employed, but these alternative PTC materials may prove too expensive for practical use in electrical connectors. 
     FIG. 2 is a view of a sample contact terminal configuration  2  that is used to demonstrate the performance of this invention when terminals are cycled in the manner shown in FIG.  1 . The sample configuration shown in FIG. 2 includes two male terminal blades  12 ,  16 . A main terminal blade  12  is connected in series to a longer auxiliary terminal blade  16  by a discrete PTC device  6 . In this configuration a PTC device having characteristics generally equivalent to a Tyco Electronics RHE 110 is employed. Leads  8  are soldered to the main and auxiliary terminal blades  12 ,  16 . These terminal blades  12 ,  16 , connected in series by the PTC device, can be mated with and unmated from two receptacle terminals  32 ,  36 , which will be connected in parallel to a common external conductor. Each of the main terminals  12  and  32 , shown in FIG. 2 can continuously carry all of the current employed herein. The auxiliary terminals  16 ,  36  carry the full current only for as long as it takes for the POLYSWITCH® device to trip or open. The two receptacle terminals  32 ,  36  can be considered to represent one terminal having multiple spring members  34 A, B and  38 A for contacting two separate blades  12 ,  16 . The auxiliary blade  16  is longer than the main blade, so it will connect first and disconnect last from the receptacle terminal assembly  30 . 
     FIGS. 3A to  3 C and FIG. 4 show the relationship between current and trip time for a connector and contact terminal using a PTC resistance device in the manner described herein. FIGS. 3A through 3C are plots showing waveforms of the voltage as mating contacts were disconnected under power. FIG. 3A shows the results of the second and tenth cycling for contacts that were cycled with two amps being carried by the mating contacts. FIG. 3B shows the results of the second and tenth cycle for the same contact configuration in which five amps were carried by the mating contacts. FIG. 3C shows waveforms for a ten amp test in which the first, tenth, thirty-third, thirty-sixth and fiftieth cycles are recorded. FIG. 3C also shows the difference between waveforms in which no arcing occurred and in which arcing occurred when the PTC material was not permitted to return to its ON condition before the contacts were again disconnected. Comparison between these waveforms in FIG. 3C, shows the effectiveness of the the PTC material. Comparison of FIGS. 3A-3C shows that the time to disconnect the two mating contact terminals differed for different currents. In other words, the unmating velocity was not the same for each waveform. Trip-time for the PTC resistance device, used herein, as a function of current is shown in FIG.  4 . 
     FIGS. 5-11 show an electrical connector assembly  4  that can be employed with the contact configuration  2  of FIG.  2  and with a discrete conductive polymer PTC device or switch  6 , such as the Tyco Electronics RHE110. FIG. 5 shows a portion of a mated header and plug connector configuration  4  in which a discrete conductive polymer PTC device  6  is employed. The discrete PTC device  6  is inserted into a pocket  48  formed on the rear or printed circuit board side of a molded receptacle header housing  42 . This pocket  48  retains the conductive polymer PTC device  6 , but it provides sufficient space to permit the PTC device  6  to expand. The leads  8  on the discrete PTC device  6  are soldered directly to a rear portion  14  of the main contact member  12  and to a rear portion  18  of the auxiliary contact member  16  In this configuration only the main contact member  12  in the header  40  would be attached directly to an external conductor on a printed circuit board. The auxiliary contact member  16  would not be connected to an external conductor through the printed circuit board. Its only contact with an external conductor would be either through the discrete PTC member  6 , or in the mated configuration, through the auxiliary receptacle terminal  36  to which it is mated. 
     FIGS. 6 and 7 show the manner in which this embodiment insures that the PTC resistive device  6  is in the proper state during disconnection of the main contact  12  and disconnection of the auxiliary contact  16 . The plug connector housing  52  and the header housing  42  of FIGS. 6 and 7 have two separate latching mechanisms that must be independently actuated in order to unmate the plug connector  50  from the header  40 . As seen in FIGS. 6-9, the plug connector housing  52  has two separate sets of two latches  54 A, B and  60 A, B. The header  40  has two sets of two latch detents  44 A, B and  46 A, B. One set of latches  54 A, B on the top and bottom of the plug connector housing  52  are engagable with and disengagable from one set of latching detents  44 A, B also on the top and bottom of the header housing  42 . A second or auxiliary set of latches  60 A, B on opposite sides of the plug housing  52  are engagable with and disengagable from a second or auxiliary set of latching detents  46 A, B on the sides of the header housing  42 . As shown in FIG. 6, the latching detent  44 A on the top of the header housing  42  is spaced further from the mating end of the header housing  42  than a latching detent  46 A, B on an adjacent side of the header housing  42 . The latching detent  44 B on the bottom of the header housing  42 , hidden in FIG. 6, is in the same axial position as the latching detent  44 A on the top of the header housing  42 . Similarly the hidden latching detent  46 B on the opposite side of the header housing  42  is at the same axial position as the latching detent  46 A on the front side of the header housing  42  as viewed in FIG.  6 . In the fully mated configuration of FIG. 7, the latches  54 A, B on the top and bottom of the plug connector housing  52  grip the top and bottom latching detents  44 A, B on the header housing  42 . 
     As seen in FIGS. 8 and 9, the plug connector latches  58 A, B and  60 A, B can be disengaged from the latching detents  44 A, B and  46 A, B by pressing on the opposite end  58 ,  64  of each latch to disengage a latching protrusion  56 ,  62  on the remote end of the latches from a corresponding detent on the header  40  The arrows in FIGS. 8 and 9 show the locations on the latches  58 A, B and  60 A, B to which force is applied to release the latches from the detents. In order to disconnect the fully mated plug connector  50  from the header  40 , it is necessary to first disengage the top and bottom or main latches  58 A, B from the corresponding top and bottom or main detents  44 A, B. As previously discussed with reference to FIG. 6, the top and bottom detents  44 A, B are further from the header mating end than the side or auxiliary detents  46 A, B. Thus in the fully mated configuration, the latch protrusions  56  and  62 , which are at the same axial position for top, bottom and side latches, will only engage on the top and bottom detents  44 A, B. Thus the top and bottom latches  58 A, B must be disengaged first. If an attempt is made to first disengage the side latches  60 A, B the plug connector  50  cannot be unmated from the header  40 , because the top and bottom main latch protrusions  56  will still engage the top and bottom main detents  44 A, B to lock the two connector halves  40 ,  50  in the fully mated configuration. 
     After the top and bottom main latches  54 A, B are disengaged from the top and bottom main detents  44 A B, the plug connector  50  can be moved in the axial direction to partially unmate the two connectors  40 ,  50 . However, a short axial movement of the plug connector  50  relative to the header  40  will bring latching protrusions  62  on the interior of the side auxiliary latches  60 A, B into engagement with the side detents  46 A, B on the header housing  42 . The side latches  60 A, B can then be manually depressed to disengage them from the side detents  46 A, B so that the mating electrical connectors  40 ,  50  can be completely unmated. However, in order to depress the side latches  60 A, B, a person seeking to disconnect the two connectors  40 ,  50  will first have to release the top and bottom latches  54 A, B and rotate his or her hand to subsequently grip the side latches  60 A, B. This manual operation will take some time. Therefore the two connectors  40 ,  50  can only be unmated in a sequential fashion with some finite time delay between disengagement of the two sets of detents  44 A, B and  46 A, B. Disconnection or unmating is therefore a two-stage process. The time delay dictated by the two separate sets of latches and protrusions is important if the connector is to disconnect a large range of currents, because it is used to insure that the PTC device  6  is in the proper state during the Main Disconnect Zone (MDZ) and the Auxiliary Disconnect Zone (ADZ) as illustrated in FIG.  1 . Release of the top and bottom latches  54 A, B corresponds to the movement of the mating contacts  2 , as shown in FIG. 2, from Stage  0  to Stage  1  as shown in FIG.  1 . In other words, disengagement of the top and bottom latches  54 A, B and detents  44 A, B allows movement of the mating contact terminals  2  through the MDZ in which the main contact  12  is disconnected from the main receptacle terminal  32 . Since the PTC resistive device  6  is in the ON state at this time, substantially all of the current formerly flowing through the main contact terminals  12  and  32  will initially flow through the PTC device  6  and through the auxiliary contact  16 , which is still connected to the auxiliary receptacle terminal  36 . This will allow the main contact to be disconnected or unmated without arcing. 
     Hand motion from the top and bottom latches  54 A, B to the side latches  60 A, B that release the side detents  46 A, B will allow the mated connector PTC to transition from Stage  2  to Stage  3  as illustrated in FIG.  1 . Then the release of the side latches  60 A, B from the side detents  46 A, B will allow the connectors  40 ,  50  to rapidly move through the Auxiliary Disconnect Zone (ADZ) to subsequently disconnect the auxiliary contact  16  from its mating auxiliary receptacle terminal  36 . Since the current flow through the auxiliary contact  16  has decayed sufficiently before movement of the auxiliary contact  16  through the ADZ, there will be no arcing when the longer auxiliary contact  16  is disconnected or unmated from the auxiliary receptacle terminal  36 . The time delay created by the sequential manipulation of the two separate set of latches will provide an adequate time for the polymeric material in the PTC device  6  to heat up due to I 2 R heating and switch the PTC device  6  to the OFF or high resistive state. This time delay will be sufficient to overcome the large difference in PTC trip time that can be expected when a specific connector design could be disconnected over a range of different currents. Identical connector assemblies can then be used in diverse applications where the current is unknown and can range from the arcing threshold for that given connector up to and perhaps momentarily beyond its maximum rated current. 
     The detents  44 A, B and  46 A, B can also function as inertial detents so that the latches  58 A, B and  60 A, B will force the connectors to one side or the other of both the MDZ and the ADZ where arcing would occur without the full range of protection provided by this contact and connector design. The connectors  40 ,  50  thus cannot be stuck in a position in which arcing could occur. The contour of these detents can also be chosen to accelerate the connectors  40 ,  50  through the MDZ and the ADZ further reducing the possibility for an arc to form. The use of inertial detents is this manner is discussed in greater detail in U.S. patent application Ser. No. 09/929,432 filed on Aug. 14, 2001, which is incorporated herein by reference. 
     A second embodiment of a connector terminal  110  implementing this invention is shown in FIGS. 12-19. This terminal  110  also includes a main contact  112 , a longer auxiliary contact  130  and a conductive polymer PTC resistive member  140  between the two contacts  112  and  130 . In this embodiment a discrete PTC device, such as a POLYSWITCH® device, is replaced by an overmolded conductive polymer that has similar active characteristics. The conductive polymer is overmolded around portions of the main and auxiliary contacts  112 ,  130 . 
     The receptacle terminal  150  used in this second embodiment is shown in FIG.  12 . The male or blade terminal  110  that mates with the receptacle terminal  150  is shown in FIG.  13 . The receptacle terminal  150  has three sets of opposed springs  152 A, B, C located on the front of the receptacle contact terminal  150 . These springs  152 A, B, C have contact points  154 A, B, C located near the distal or front ends of the springs, which each comprise curved cantilever beams. A crimp section  156  is located on the rear of this receptacle terminal  150 , and a single external conductor or wire can be crimped to this receptacle terminal. 
     The male or blade terminal  110 , shown in FIG. 13, has two main contact blades  114 A, B located on opposite sides of the longer auxiliary contact  130  located between the two main blade contacts  114 A, B. The auxiliary contact  130  is attached both physically and electrically to the main contacts  112  by the overmolded PTC conductive polymer  140 . Each of the contacts  112 ,  130  extend forward from the conductive polymer  140  into a position in which they can be inserted into engagement with the springs  152 A, B, C on the mating receptacle terminal  150 . This blade terminal  110  also extends from the rear of the overmolded conductive polymer  140  with printed circuit board leads  126  located at the rearmost extent. This rear section  124  is part of a single stamped and formed member that also includes the two main contact sections  114 A, B. The auxiliary contact  130  is a separate piece that is mounted on to this main contact terminal  110  by the overmolded PTC conductive polymer  140 . 
     FIGS. 14-16 show the matable blade terminal  110  and receptacle terminal  150  of FIGS. 12 and 13. As shown in FIGS. 14-16, the receptacle terminal  150  also includes a separate sleeve  158  that surrounds the base of the terminal  150  and includes back up beams  159 A, B supporting the outermost springs  152 A, B that engage the main contact sections  114 A, B of the blade terminal. These backup beams  159 A, B increase the contact force between the main contact blades  114 A, B and the receptacle terminals  150 . During normal operation, the main contact  112  will carry most if not substantially all of the current carried by the mating connectors  104  and  106 , first indicated in FIG. 20, and this additional contact force will improve the performance of the connectors. The central springs  152 C, on the receptacle terminal  150 , are not backed up by beams extending from the sleeve  158 . These central springs  152 C will only engage the auxiliary blade contact  130 , which during normal operation will only carry a relatively insignificant current. Only momentarily, during mating and unmating, will the auxiliary contact conduct any significant current, so back up beams are not necessary. 
     FIG. 17 shows the stamped and formed metal auxiliary blade contact  130 , and FIG. 18 shows the stamped and formed main contact  112 . The auxiliary contact  130  includes a contact section  132  in the form of a standard blade that is typically used to mate with a receptacle terminal  150  having spring beams  152 C to engage the blade section  132 . The auxiliary contact  130  will typically be plated in the blade contact section  132  so that a reliable electrical contact can be established. The auxiliary contact also includes a transverse cross member  134  located at the rear of the blade contact section  132 . This cross member  134  is in a plane that is offset and is parallel relative to the plane of the auxiliary blade contact section  132 . The blade contact section  132  is joined to the cross member  134  by an intermediate section  136  that extends between the two planes of the two primary elements of the auxiliary contact. The cross member  134  is spaced from the blade contact section  132  so that the cross member  134  will also be spaced from the main contact  112  to provide space for the PTC conductive polymer  140  that will be positioned between the auxiliary contact  130  and the main contact  112 . 
     The main contact  112  is an essentially flat stamped and formed metal member that has two main contact sections  114 A, B that are spaced apart on opposite sides of a central cutout  116  that extends from the front of the main contact  112  to a middle section  118 . The width of this cutout  116  is sufficient to receive the blade contact section  132  of the auxiliary contact  130  and to provide an adequate separation between the auxiliary blade section  132  and both main contact blade sections  114 A, B. A rear section  124  of the main contact  112  extends from a rear edge  120  of the middle section  118 , and includes two pins or leads  126  that can be inserted into through holes in a printed circuit board to connect external conductors on the printed circuit board to the main contact  112 . There is no direct connection between external conductors to the auxiliary contact  130 , other than through the overmolded PTC conductive polymer  140  or when connected to the mating receptacle terminal  150 . The main contact terminal  112  also includes two notches  122  on opposite edges to provide surface for securing the main contact  112  to the PTC conductive polymer  140 . 
     FIG. 19 demonstrates the manner in which the PTC conductive polymer  140  can be overmolded around the auxiliary contact  130  and main contact  112 , or alternatively in which the two contacts  112 ,  130  can be insert molded in the PTC conductive polymer  140 . Each of the contacts  112 ,  130  are mounted onto a carrier strip  128 ,  138 . FIG. 19 shows these two carrier strips  128 ,  138  and pilot holes  129 ,  139  in each carrier strip. These pilot holes  129 ,  139  provide a means for properly locating the two contact members  112 ,  130 . The two aligned contact members  112 ,  130  are then positioned in a mold cavity. Since the auxiliary blade portions  132  and the two main contact blade sections  114 A, B are in the same plane, the mold can be easily closed around these planar members. The conductive polymer can then be molded in surrounding relationship relative to the portions of the auxiliary contact  130  and main contact  112  that are positioned in the mold cavity. After the conductive polymer has sufficiently cooled to solidify, the contact assembly can be removed from the mold cavity and the carrier strips  128 ,  138  can be removed at the appropriate time. This will leave a blade terminal assembly  102  that can be mounted in an electrical connector housing, such as a header housing  200  having many of the characteristics of a conventional printed circuit board header. 
     The embodiment of FIGS. 12-19 is representative of an integrated terminal or contact including a main contact, an auxiliary contact and a PTC conductive polymer. An integrated terminal or contact can be fabricated by means other than the overmolding or insert molding fabrication method illustrated by this specific embodiment. For example, it is not necessary to mold the PTC conductive polymer in surrounding relation to both the main and auxiliary contacts. PTC material or a PTC device only needs to be located between the main and auxiliary contacts. An integrated device can be fabricated by bonding a PTC device between the two contacts. A PTC device may be secured to the contacts by soldering the PTC device to one or both contacts or by using a conductive adhesive or other conductive interconnection means. The integral terminal assembly could be formed by first molding the PTC conductive polymer in a shape so that it would conform to both terminals, which would then be positioned in engagement or close proximity to the molded PTC device and then secured or bonded to form an electrical connection. Molding would not be the only process that could be used to form a discrete PTC device that is then to be incorporated into an integral assembly. For example, some other fabrication technology would be employed for nonpolymeric PTC materials. Another fabrication technique would be to mold the PTC material between the two contacts, but not in surrounding relationship. Another approach would be to place one of the contacts in a mold and then mold the PTC conductive polymer in contact with this one contact or terminal. The other contact or terminal could then be bonded to the PTC polymer by solder, conductive adhesive or some other conductive bonding agent. Additionally the structure of the main and auxiliary contacts used in the embodiment of FIGS. 12-19 is merely representative, and other integrated contacts may include contacts or terminals of different construction or shape. For example, only one main contact may be needed in other configurations. Furthermore, other embodiments might employ female or receptacle terminals that are part of an integral terminal device including a PTC device or PTC conductive material. FIGS. 20-37 show details of the electrical connector housings  160 ,  200  and the electrical connectors  104 ,  106  in which the receptacle terminal  130  and blade terminal  110  of this second embodiment could be employed. The blade terminal  110  is positioned within a header housing  200  of generally conventional construction, except for provisions unique to the blade terminal  110  depicted in FIGS. 13-16. The receptacle terminal  150  shown in FIG. 12 is mounted in a plug connector housing  160  that is matable with the header housing  200 . FIG. 20 shows that the receptacle terminal  150  and the blade terminal  110  can be employed in connectors that also include conventional receptacle terminals and blade terminals that are employed on circuits where the current would always be below the arcing threshold for that type of terminal. 
     The embodiment of FIG. 20 also includes a lever  180  that functions as a mechanical assist member to overcome forces resisting mating and unmating of the two electrical connectors  104 ,  106 . The lever  180  is mounted on the plug connector housing  160  and engages the header housing  200  so that rotation of the lever  180  moves the plug connector  106  relative to the header  200 . However, as will be subsequently discussed in more detail, the lever  180  does not move the two connectors  104 ,  106  completely from a fully mated position to a fully unmated position, nor does it move the two connectors from a fully unmated position to a fully mated position. FIG. 21 shows the two connectors  104 ,  106  in a fully unmated configuration and FIG. 22 is a view of a fully mated configuration. Comparison of these two views shows that the lever  180  is rotated in a clockwise direction to fully mate the two connectors  104 ,  106 . 
     FIGS. 23 and 24 show the manner in which the lever  180  can be mounted on the plug connector housing  160 . The lever has two arms  182  that are joined by a central handle  184  in the form of a crosspiece extending between ends of the arms  182 . Each lever actuation arm  182  includes a pivot pin  190  located on the interior of the arm, intermediate their opposite ends. These pivot pins  190  fit within sockets  170  on the sides of the plug connector housing  160 . The sockets  170  are formed in a sleeve  166  that surrounds the sides of the main body  162  of the plug connector housing  160 . Each socket  170  has a circular bearing surface  172  that is interrupted by a slot  174  that extends inwardly from the mating face  164  of the plug housing  160 . Each arm  182  also includes a finger  194  at its distal or free end. A cam arm  192  is located on one side of each pivot pin  190 . As will be subsequently discussed in greater detail, these cam arms  192  will fit within cam grooves  208  on the header housing  200  to impart relative movement between the plug connector  106  and the header  104  as the lever  180  is rotated. 
     The plug connector housing  160  also includes an auxiliary housing latch  196  located on the top  198  of the housing  160  shown in FIG.  23 . There is an inertial detent on housing  160  that is opposite to the housing latch  196 . The mechanical assist lever  180  is used to disconnect the main blade contacts  114 A, B from the mating receptacle terminal  150  in the plug connector  106 . The auxiliary latch  196  must be activated to disconnect the auxiliary blade contact  130  from the mating receptacle terminal  150 . 
     The molded header housing  200  that mates with the plug connector housing  160  is shown in FIG.  25 . This header housing  200  has a header shroud  202 , which forms a cavity  204  in which at least one arc-less blade terminal  110 , such as that shown in FIGS. 13 and 14 is located. Other terminals, typically in the form of male pins, could also be located within this cavity  204 . These other conventional male pins would mate with conventional receptacles and would be used in circuits that would not carry sufficient current or electrical energy to create an arc. Alternatively, more than one arc-less blade terminal  110  incorporating this invention could be located in the header  104 . 
     A cam follower groove  208  is located on each exterior side of this header shroud  202 . Only one cam follower groove  208  is shown in FIG. 25. A mirror image cam follower groove is hidden from view on the opposite side of the view of the header housing  200  shown in FIG.  25 . These cam follower grooves  208  are dimensioned to receive the cam arm  192  located on the lever  180  that is mounted on the plug housing  160 . The cam arms  192  engage surfaces of these grooves as the lever  180  is rotated between first and second positions. When the lever  180  is rotated to fully mate the two connectors, each cam arm engages the surface  210  of the cam groove  208  closest to the mating end of the header. When the cam arm  192  is rotated in the opposite direction, the cam arm engages the other side  212  of the cam groove  208  to cause relative movement of the two connectors  104 ,  106  from a fully mated configuration to a configuration in which the shorter main contacts  114 A, B are disengaged or disconnected, but the auxiliary contact  130  still engages its mating receptacle contact terminal  150 . Guide rails  218  are included on the interior and exterior surfaces of the shroud  202  to insure that the mating connectors  104 ,  106  move parallel to a mating axis during unmating and mating. These guide rails  218  also comprise reaction surfaces, which prevent the cam arms  192  from becoming disengaged from the corresponding cam grooves  208 . 
     A sloping surface  216  is located adjacent to and slightly to the rear of each cam groove  208 , as shown in FIG.  28 . Both the cam grooves  208  and these sloping surfaces  216  are formed on a rib  214  protruding from the exterior side face of the header shroud. The sloping surface  216  extends laterally outward of the portion of the rib  214  in which the cam groove  208  is formed. These sloping surfaces  216  are located in positions so that they will engage the fingers  194  located at the distal ends of the two lever arms  182  to force each lever arm  182  outward so that the fingers  194  can clear front edges  168  of the plug connector sleeve  116  so that the lever  180  is free to move. The manner in which the lever arms  182  are unlocked, and the significance of this feature, will be subsequently discussed in greater detail. 
     Two latching grooves  220  are located on the top surface of the header housing  200  when viewed from the perspective of FIG.  25 . These latching grooves  220  receive latching clips  186  on the lever handle  184  to lock the lever  180  in place when the connectors are fully mated. These clips  186  can be disengaged by depressing a projection  188  on the lever handle  184 . The header shroud  202  also includes two detents  222 ,  224  projecting from the upper surface. Identical detents project from the lower surface of the header shroud. These detents  222 ,  224  engage opposed surfaces on the interior of the plug connector sleeve. These detents function in the same manner as those shown in U.S. patent application Ser. No. 09/929,432 filed on Aug. 14, 2001 incorporated herein by reference. The first or inner detent  222  engages a surface on the plug connector sleeve  166  to hold the connectors in fully mated configuration. A force applied to the lever  180  is sufficient to cause slight deformation of the connector housings to permit the connectors to move to a fully mated configuration. Similarly, a force applied to the lever  180  in the opposite direction overcomes the latching effect of this inner detent  222  so that the connectors  104 ,  106  can be moved from a fully mated configuration to an intermediate configuration in which the main contacts  12  have been disconnected, but in which the auxiliary contact  130  remains in engagement with the receptacle terminal  150 . At this point the auxiliary plug connector housing latch  196  engages the second or outer detent  224 , which is laterally offset relative to the first detent  222  and which is closer to the mating end of the header connector  104 . Further rotation of the lever  180  cannot then disconnect the connectors because of the engagement between the auxiliary latch  196  and the second or outer detents  224 . At this point an operator must press the opposite end of the auxiliary latch  196  located on the top of the plug connector housing  160 . There is an inertial detent that can be overcome with increased unmating force. The top latch is the only cantilever beam that must be depressed by the user. The inertial detent on the bottom of the connector is necessary to insure that the auxiliary contact unmates or disconnects quickly and cleanly through the Auxiliary Disconnect Zone (ADZ).) The lever  180  will have rotated sufficiently to expose latch  196 , but it will take some time for the operator to change hand position from the lever  180  to the top auxiliary latch  196  and depress it in order to fully unmate the connectors. This time delay will be sufficient for the I 2 R heating to switch the PTC conductive polymer  140  from an ON, or low resistance state, to an OFF or high resistance state. This delay will also be sufficient to allow the current flow through the auxiliary contact  130  to drop below the arcing threshold, regardless of the initial current flowing through the connector, and the trip time of the PTC conductive polymer  140 , or other PTC devices. After the auxiliary latch  196  has been disengaged and the inertial feature has been overcome, then connectors  104 ,  106  can be fully disconnected and separated. 
     FIGS. 29-32 show the manner in which the two connectors  104 ,  106  are mated. FIGS. 33-37 show the unmating steps. To mate the two connectors  104 ,  106  it is first necessary for an operator to push the two connectors  104 ,  106  into partial engagement. Since the header  104  will normally be fixed to an electrical component, and may be mounted on a fixed bulkhead or panel, this step will normally require the operator to grasp the plug connector  106 , which will normally be attached to wires or on the end of a wire harness. The operator will align the two connectors and then push the plug connector  106  into partial engagement with the header connector  104 . There will, of course, be no functional difference if the receptacle is a bulkhead mounted configuration attached to wires. There is also no relevant difference if the receptacle is a free-hanging cable version except that both connectors must probably be grasped to accomplish the mating operation. The auxiliary latch  196  will ride up and over the detent  224 . (The inertial feature located opposite to the auxiliary latch  196  must also be overcome.) The end of the auxiliary contact  130  will engage the receptacle terminal  150 . If the circuit to which either terminal  110 ,  150  is attached is live, some current will initially flow through the auxiliary contact  130 , and there will be a make spark as the auxiliary contact  130  engages the receptacle terminal  150 . A make spark is benign compared to a breaking arc and will not cause significant damage. Assuming that current initially flows through the auxiliary contact  130  at this point, the PTC conductive polymer  140  will also conduct since it will be in the ON or RESET state prior to mating. If the current is high enough the PTC conductive polymer  140  will trip to the OFF condition. If the initial current is not sufficient to trip the PTC conductive polymer  140 , then the PTC conductive polymer  140  will remain in the ON state. The operator will not be able to push the connector  104 ,  106  to their fully mated configuration because the cam profiles for the lever mechanism  180  will prevent further movement of the connector unless the lever is rotated. Just prior to engagement of the main contacts  112  with the receptacle terminal  150 , the fingers  194  on lever arms  182  will engage the sloping surfaces  216  on the exterior of the header shroud  202  to force the lever arms  182  outward and free the lever arms  182  from abutting edges  168  of the plug housing sleeve  166 . The lever  180  can now be rotated to its fully engaged position as shown in FIGS. 31 and 32 in which the main contacts  112  will be fully mated with the receptacle terminal  150 . If the connectors  104 ,  106  are mated in a live state with sufficient current to have caused the PTC resistive material to switch to its OFF state prior to their engagement, a make spark will also occur as the main contacts  112  engage the receptacle terminal  150 . The make spark, however, will not cause any significant damage because of its benign nature compared to a breaking arc. In any event, once there is a low resistance path established between the main contact blade sections  114 A, B and the receptacle terminal  150 , only a small amount of current will be allowed to flow through the auxiliary contact  130  and the PTC conductive polymer  140 . If the PTC conductive polymer  140  had been in the OFF state, then connection of the main contacts  114 A, B to the receptacle terminal  150  would sufficiently reduce the current through the PTC conductive polymer  140  to allow the PTC conductive polymer  140  to cool and reset to an ON state. The PTC conductive polymer will then be able to protect against an arc when unmating of the connectors  104 ,  106  breaks a live circuit. This cooling and recovery to the low resistance state occurs very quickly, on the order of seconds or less in typical applicable devices. 
     The first step in the unmating procedure is to depress the release projection  184  to permit rotation of the mechanical assist lever  180 . The arrow in FIG. 31 shows the direction in which a force is applied to this release projection. After the release projection is disengaged, the lever  180  can be rotated in a clockwise direction as shown in FIG.  33 . Movement of the lever  180  from the position shown in FIG. 31 to the position shown in FIG.  33  and finally to the position shown in FIG. 35 will disengage the main contact  112  from the receptacle terminal  150 . Referring to FIG. 1, this will shift the main contact blade sections  114 A, B from Stage  0  through the Main Disconnect Zone (MDZ) to Stage  2 . The inner detent  222  on the header housing  200  and a corresponding detent or raised surface on the interior of the plug connector sleeve  166  will also prevent the two connectors  104 ,  106  from staying in the MDZ where the contacts either remain in contact, or experience intermittent touching which could establish an arc between the main contact  112  and the receptacle terminal  150 . There is another detent for the main contact that is a mirror image of detent  222  located on the bottom of the header. The unmentioned detent is on the opposite side and shifted off center to distribute the load evenly. This detent is important because one detent would create instability. If this time is prolonged the PTC conductive polymer  140  could switch to the OFF state and permit an arc to be developed. The shape of these detents  222  will force the connectors away from the MDZ. Once the lever  180  has been moved to the position shown in FIG. 36, the auxiliary latch  196  will be exposed, and the operator will be able to actuate that latch. This auxiliary latch  196  must be depressed so that it can clear the second detent  224 , and an inertial detent for the auxiliary contacts that is located on the opposite side as the latch, located closer to the mating end of the header housing  200 . The time that it would take an operator to disengage the auxiliary latch  196 , after first rotating the lever  180 , will be sufficient for the current passing through the PTC conductive polymer  140  to be reduced to a level where an arc will not be generated when the auxiliary contact  130  is disconnected. In other words, the PTC Opening Zone will last long enough for the PTC to open regardless of the current flowing through the connector when unmating begins. The current will be low enough so that a damaging arc will not be generated as the auxiliary contact  130  moves through the ADZ (auxiliary disconnect zone). After the connectors have moved through these states, the plug connector  106  will be completely unmated and separated from the header as shown in FIG.  37 . 
     FIG. 38 shows the damage that can result from arcing for a conventional contact that has been disconnected one time with a purely resistive load at 59 volts, 60 amperes without the use of the PTC resistor of the instant invention. Note the damage to the spring members in the mating connector. FIG. 39 shows a similar contact that has been disconnected fifty times with a purely resistive load at 59 volts, 60 amperes using a PTC in accordance with this invention. Both mating contacts are undamaged. The auxiliary contact in the protected version is also undamaged since there was only leakage current flowing through the auxiliary when it separated from the mating contact. Comparison of FIGS. 38 and 39 will show that even though the PTC resistor is attached to the male contact, protection is also afforded to the female contact. It should be understood, however, that the PTC resistor and the auxiliary contact can be employed on the receptacle side and that the main and auxiliary contacts need not be male members. 
     FIGS. 38 and 39 show the effects of the conductive polymer PTC device to prevent arcing damage when a connector assembly is used with a purely resistive load. Inductive loads can be expected to cause over-voltage spikes when the connectors are disconnected while high currents are flowing. If the PTC device can withstand those voltage spikes, the arc protection will work exactly as previously described. If the PTC device cannot withstand the voltage spikes, then it can be destroyed unless it is protected from those over-voltages by utilizing an over-voltage protection device such as an MOV, zener diodes or spark-gaps. Alternatively, the inductive load can have the over-voltage protection devices across it and there will again be no destructive over-voltage exposure for the PTC device. FIGS. 40 and 41 shows the manner in which a surge suppressor can be connected in parallel with the PTC device in a connector assembly according to this invention as well as in parallel with an inductive load to compensate for these voltage spikes. 
     Separation velocity is controlled in each of the representative embodiments of this invention by employing a two step unmating procedure that results in a sufficient time delay to allow the conductive polymer PTC device to turn OFF before the auxiliary contact is disengaged. Means are also provided in the preferred embodiment that will insure that the main contacts are quickly disconnected before the PTC member is able to switch to the OFF condition. The representative means discussed herein are not the only means of separation velocity control that can be employed. The unmating velocity of a manually operated electrical connector can be controlled in different ways. Also, if the load current range is limited, meaning that there is a minimum current that can flow, which is a significant percentage of the maximum current, the delay caused by the additional length of the auxiliary contact can be sufficient, causing a distinct 2-step disengagement to be unnecessary. 
     Other approaches exist to cause some resistance that the human operator must overcome when disconnecting a mating connector. One such example is shown in FIGS. 42A-42D, which shows a receptacle connector  304  and a mating plug connector  306  which includes a means for providing rapid unidirectional movement through the contact disconnect zones and the time delay between them with a single lever. This alternative lever configuration can provide unidirectional high velocity through the MDZ and the ADZ, while also providing a time delay between those zones without an additional latch. The high velocity is generated as the loaded cantilever beam  316  on the lever  308  pushes the plug pin  310  through the receptacle housing detents  312 ,  314  in a housing channel  318  as shown in FIGS. 42A and 42C. As shown in FIG. 42B, the time delay is caused when the cantilever beam  316  on the lever  308  relaxes after pushing the plug pin  310  through the first receptacle housing detent  312  and then is re-flexed or reloaded by continuing motion of the lever  308  until it can push the plug pin  310  through the second receptacle housing detent  314 . 
     In other versions, a detent, or spring release feature, would also preload the human force to the level necessary to guarantee a sufficient velocity over the critical separation zones. Pistons, or dashpot devices, can provide controlled resistance that can slow velocity and additional latching mechanisms or levers can force momentary stops between the separation of the main and auxiliary contacts if necessary. Other means would also be apparent to one of ordinary skill in the art. 
     This invention is also not limited to a conductive polymer PTC device. Other positive temperature coefficient resistance devices exist that could be substituted for the conductive polymer PTC devices or materials that are used in the preferred embodiments discussed herein. Metallic PTC devices are know to exist which could be employed in alternate embodiments that employ all of the basic elements of this invention. Other PT materials such as doped-BaTiO 3  might also be employed, although the expense of these various alternatives may prevent them from comprising an acceptable commercial alternative to the use of conductive polymer PTC devices and materials. Other alternative embodiments would be apparent to one of ordinary skill in the art. Therefore the invention, described herein in terms of representative preferred embodiment, is not limited to those representative embodiments, but is defined by the following claims.