turning now to the drawings in more detail , fig1 shows an electromagnetic circuit breaker incorporating certain features of the present invention and mounted in a panel p by means of two screws s , s so that a toggle or handle 10 can be used to reset the breaker after it has been tripped . the circuit breaker housing comprises two molded plastic half sections , only one of which is shown as the rear section 12 in fig1 . the front half section 13 has been omitted for clarity from this view . these half sections are riveted to one another as indicated generally by the rivets r , r . the screws s , s are provided in captive nuts n , n provided between these half sections to support the breaker in the panel in accordance with conventional practice . these housing half sections define an internal cavity where the circuit breaker mechanism is mounted . this mechanism comprises a collapsible toggle link mechanism 14 that is used to couple the handle 10 to a contact lever 16 , shown closed in full lines and open in broken lines . this collapsible toggle mechanism may be of conventional configuration such as that depicted in issued u . s . pat . no . 4 , 347 , 488 . the circuit breaker operation provides for collapsing the toggle mechanism 14 through movement of an armature 18 from the solid line position shown to the broken line position as a result of magnetic forces induced in the frame 20 and in the movable magnetic solenoid core c and in the pole piece q . magnetic flux created as a result of an over current / over voltage in the coil 22 pulls the core c upwardly in the delay tube t with the result that pole piece q pulls armature 18 downwardly toward it causing the other end of the armature 18 to act through a mechanical sear ( not shown ) but indicated schematically at 24 so as to collapse the link 14 and allow the spring loaded contact lever 16 to move from its solid line position to its broken line position opening the contacts 16a and 50 . the movable contact 16a on contact lever 16 moves upwardly on opening to define a path of movement indicated generally by the arrow and associated phantom line in fig1 . the contact 16a and lever 16 are shown in closed position in full lines and in open position in broken lines . as the contact 16a on the movable contact lever 16 follows this path of movement during an overload condition , it is important to prevent the resulting electric arc produced from reaching the mounting panel p and / or other metal components of the breaker mechanism itself . consequently , an arc chamber is provided for the movable contact 16a with the following characteristics . in addition to the dielectric plastic half sections for the molded circuit breaker case laterally spaced front and rear insulated boards 30 of fish paper or the like are provided , as indicated generally at 30 in fig1 and these boards 30 are slotted to receive u - shaped metal grid elements that are preferably made from steel . these grid elements 32 , 32 serve to extinguish the arc from the opening contacts and to dissipate the heat generated on opening at high overload conditions . the space between these grid elements provides openings for the discharge of the gases produced so that the pressure produced can be dissipated through a metal mesh screen indicated generally at 34 . the screen 34 is supported by these parallel insulating boards , 30 , 30 in much the same manner as these boards 30 support the u - shaped grid elements 32 , 32 . the arc chamber further includes an outer end wall 36 and the outer end wall defines an opening for the screen 34 as best shown in fig4 . the arc chamber further includes an integrally formed top and inner end wall defined by a bent sheet of insulated board material . the inner end and top walls have a shape suggestive of the numeral 7 . the top wall is indicated generally at 40a and the inner end wall at 40b . the latter includes an inclined lower end portion 40c that is slotted to receive the two parallel arms 16b and 16c of the movable contact lever 16 as best shown in fig3 . the lower end portion of the inner end wall is provided in aligned slots 12s of the housing bottom wall and is provided between the fixed contact 50 and adjacent rivet r so as to increase the dielectric strength of the resulting breaker in the area of the arc chamber . the fixed contact 50 is provided on a bent terminal bar 52 that supports a conventionally configured connector 54 so that a wire w can be secured to the connector 54 to provide an electrical connection between the wire w and the fixed contact 50 on the terminal bar 52 . the terminal bar 52 is preferably fitted with a steel shoe 56 which shoe includes an upturned end portion for deflecting the hot gases away from the terminal bar 52 and directing these gases upwardly in the arc chamber where they can be dissipated and ultimately discharged through the screen 34 referred to previously . the shoe 56 also draws the arc off of the stationary contract and onto its cooler surface . in essence this shoe 56 also acts as an arcing horn on the stationary contact terminal . slots 12v and 13v are provided in the end wall of the circuit breaker housing half sections 12 and 13 so as to provide an exit for these gases after they have been so dissipated as best shown in fig5 . the inner wall of the arc chamber and more particularly the lower portion 40c thereof is canted so that the lower end portion is received in the slots 12s defined by the housing half sections . this lower portion 40c is oriented generally perpendicular to the arcing horns or grid elements 32 or parallel to the path of contact 16a as referred to previously . the fixed contact and more particularly the lower end portion of the terminal bar 52 and the shoe 56 define the lower portion of the arc chamber and it is important to note that the lower portion 40c of the inner wall cooperates with the outer wall 36 to define an upwardly divergent lower region of this arc chamber in order to dissipate the gasses and plasma generated by the breaker &# 39 ; s opening contacts in a generally upward direction toward the metal screen 34 and the vents 12v and 13v referred to previously . both the inner wall 40 and the outer wall 36 of the arc chamber are supported in slots provided for this purpose in the circuit breaker housing half sections 12 and 13 and it should be noted that the upper portions of both the inner and outer arc chamber walls are so spaced apart as to provide an arc chamber upper portion of greater volume than the lower arc chamber portion defined by the lower portions thereof . this geometry provides improved dielectric strength for the breaker as between the terminal strip 52 and fixed contact 50 and the rivet r . turning next to a discussion of the electromagnetic structure that serves to trip the armature 18 , fig1 shows the armature 18 in two positions ; one corresponding to the contact closed condition ( that is the solid line position for armature 18 ) and the other for the armature tripped condition ( shown in broken lines corresponding to the contacts open position also illustrated in broken lines in fig1 ). this electromagnetic structure includes the steel frame 20 that pivotally supports the armature 18 and that also supports the contact lever 16 and the handle 10 in accordance with conventional circuit breaker manufacturing techniques . the frame 20 also supports delay tube t by means of an annular fastener 62 and the delay tube is provided with a pole piece q at its upper end so that the electromagnetic coil 22 surrounding the delay tube t is adapted to pull the plunger or core c upwardly against the downward force of a return spring 63 provided between the pole piece q and a shoulder of the plunger or core c . the delay tube t may be filled with a damping fluid such as oil in order to reduce the speed of movement for the plunger or core c and hence to increase the time required for tripping of the armature 18 . the coil 22 is supported between flanges 60a and 60b of a plastic molded bobbin 60 and it is an important feature of the present invention that the bobbin 60 also includes an upwardly extending collar portion 60c that surrounds the pole piece q and that serves to space the upper end of coil 22 from the end of the pole piece q that is adapted to being engaged by the armature 18 . turning now to a more detailed description of fig2 it will be noted that the circuit breaker housing half sections 12 and 13 are identical to those provided in the circuit breaker assembly of fig1 except for the barrier b that isolates the terminal 54 from that of an adjacent circuit breaker terminal ( not shown ). this barrier can be formed or not formed in the process of molding the breaker half sections simply by removing or inserting a mold insert ( not shown but shaped to fill the mold cavity that forms this barrier b ). furthermore , the arc chamber construction is identical to that of fig1 save only the actual configuration of the terminal bar 152 provided for the fixed contact 50 . where the fig1 circuit breaker assembly is designed to accommodate connecting wires w , w at the sides of the housing the fig2 circuit breaker assembly is designed to accommodate connections at the bottom of the circuit breaker housing , as indicated generally at x and y in fig2 . however , the electrical connections to the coil 22 in fig2 are identical to the connections provided for in fig1 . that is , the movable contact lever 16 is connected by means of a braided wire 64 to one end of the coil 22 and the other end of the coil 22 is connected by means of braided wire 66 to the opposite terminal y in fig2 . fig1 shows coil 22 connected to the terminal bar 53 by a wire 68 . thus , the breaker in fig2 operates in substantially the same manner as that described above with reference to fig1 in that the armature 18 is pulled or tripped by electromagnetic flux created between pole piece q , core c and frame 20 as a result of over current / over voltage conditions created in the coil 22 . fig2 further includes a relay coil 122 provided on a smaller auxiliary plastic bobbin 160 . opposed flanges 160a and 160b are provided in the bobbin 160 . a center opening in the auxiliary bobbin permits it to be received on the primary bobbin 60 . the collar portion 60c of the primary bobbin 60 is designed to so receive auxiliary bobbin 160 in order to permit installation of the relay coil 122 on any circuit breaker equipped with a bobbin 60 such as that shown and described above with reference to fig1 . the relay coil 122 is provided in a separate control circuit by leads 164 and 168 associated with the ends of the wire in coil 122 . these leads 164 and 168 are each connected to associated terminals z1 and z2 so that the relay coil 122 can be used to remotely trip the breaker mechanism while the primary coil 22 carries the normal load current that is not enough to produce a magnetic flux situation in the frame , the pole piece and the plunger c to achieve tripping of the armature 18 . as a result of the above - described bobbin configuration , it will be apparent that a single design circuit breaker housing assembly can be provided to accommodate a relay coil in one version of the breaker without the necessity for substituting bobbins , and in the straightforward assembly of fig1 the pole piece q preferably has its lower face located in approximately the same plane as that defined by the adjacent flanges 60a and 160a of the primary and auxiliary bobbins or spools . turning next to a more detailed description of the terminal configurations provided for in the circuit breakers of fig1 and 2 , it will be recalled that the wires w , w connected to the terminals 52 and 53 of the circuit breaker housing are received at the ends of the housing and more particularly are received in connectors 54 provided for this purpose . this geometry may be required where the backspace behind the panel p is limited , or where the type of connectors 54 are required to accommodate larger size wire w . in fig2 on the other hand , the terminals x and y associated with the fixed contact and the electromagnetic coil 22 respectively are in the form of studs that carry nuts and washers to facilitate securing conductive leads or wires ( not shown ) at the bottom of the circuit breaker housing . obviously , the studs 154 and 156 could be provided instead of the terminal bars 52 and 53 in the circuit breaker housing assembly of the fig1 breaker . as shown in fig2 additional studs 158 and 159 are provided in the circuit breaker housing assembly of fig2 . as mentioned previously , the additional two auxiliary studs 158 and 159 are available for providing electrical connections to the relay coil 122 in the fig2 breaker . in further accordance with the present invention a molded terminal strip 170 is provided on the bottom wall of the circuit breaker housing to support the auxiliary terminals 158 and 159 . this molded terminal strip 170 includes openings for receiving and self - supporting these auxiliary terminals 158 and 159 , and this molded strip 170 is held in place by the studs 154 and 156 associated with the fixed contact and primary coil 22 respectively . the studs 154 and 156 have upper ends that define downwardly facing flanges that engage abutment surfaces provided around the openings 153 and 155 to permit these studs 154 and 156 to be secured in place by the nuts 174 , 174 . the molded terminal strip 170 has upstanding integrally defined locating studs 171 and 172 adjacent each end , which studs are adapted to be received in complementary shaped openings 173 and 175 respectively defined for this purpose in the molded circuit breaker half sections ( fig1 shows these openings and fig2 shows the locating studs provided in the openings ). with reference to the circuit breaker half sections and more particularly with reference to the bottom wall defined thereby , fig1 shows a molded switch case 180 provided in an opening defined centrally of the bottom wall of the switch case half sections 12 and 13 . this molded switch case 180 includes flanges 182 and 184 that are received in slots indicated generally at 183 in fig2 so that a conventional limit switch 190 can be provided in the molded switch case 180 as suggested in fig1 . the limit switch 190 is of conventional configuration having three terminals 192 , 194 and 196 that permit remote indication of the circuit breaker &# 39 ; s condition through a mechanism provided between the plunger 198 of the limit switch 190 and the underside of the movable contact arm or lever 16 of the circuit breaker mechanism . a cantilever spring 200 is provided in the molded switch case 180 and , more particularly , has its fixed end portion 200a provided in a slot defined by the molded switch case 180 so that the free end of the cantilever spring 200 can itself support a molded plastic button 202 that is secured to the free end of the spring 200 and is adapted to be engaged by the underside of the movable contact lever 16 of the circuit breaker mechanism . thus , as the contact lever 16 moves from the solid line to the broken line position illustrated in fig1 the resilient spring 200 will cause the button 202 to follow the lever 16 and allow the plunger 198 of the limit switch 190 to move upwardly so as to enable an indicating circuit ( not shown ) for remote indication of the circuit breaker &# 39 ; s condition .