a spherical ball 85 balls 85 being biased toward contact carrying member 75 by springs 87 v shaped cam surfaces 81 balls 85 and bias springs 87 form an overcenter arrangement for the contact carrying member 75 a pair of flanges 89 are formed on contact carrying member 75 each of the flanges 89 being adapted to engage an arm 69 to interconnect triggering member 57 and contact carrying member 75 each of the flanges 89 has a central opening 91 through which an arm 69 may easily pass however openings 91 prevent passage of enlarged head portions 71 each of the flanges 89 has a pair of sloping cam surfaces 93 to mate with the sloping cam surfaces 73 on enlarged head portions 71 due to a certain amount of flexibility in the extending arms 69 forcing contact carrying member 75 toward triggering member 57 to engage the mating sloping cam surfaces 73 and 93 will permit the enlarged head portions 73 to pass over flanges 89 and snap into the interlocking position with arms 69 in central openings 91 extending contact supporting portion 77 of contact carrying member 75 has a pair of slots 95 formed to extend along the length of this portion so that portion 77 is divided into two parts 97 as a result of the slots 95 the parts 97 have a certain degree of flexibility when the contact carrying member is not located on portion 53 of the plunger a passageway 99 having a rectangular cross sectional area extends through both.