as shown in fig1 , a headlamp comprising light source housing 10 , is supported on a vas shroud 12 , adapted to be attached to a military helmet ( not shown ) by fasteners inserted through fastener holes 14 in the shroud . the headlamp can be any of various portable headlamps . in the embodiment shown , the light source housing includes four light - emitting diodes ( leds ) 16 disposed behind a transparent cover 18 . the housing also includes a set of electrochemical cells not shown , an operating push - button 20 , and electronic circuitry responsive to the push - button for turning the leds on and off , regulating the amount of illumination emitted by the leds , ensuring that initial brightness is maintained , and providing for selection of a repeating flashing mode . the light source housing 10 has a pair of aligned supporting pins extending laterally in opposite directions from locations on the lower parts of the sides of the housing 10 . one such pin is pin 22 in fig1 . the other pin is not shown in fig1 . the pins cooperate with pin - receiving holes in ears protruding forward from the shroud to form a hinge on which the light source housing is pivotable about a horizontal axis corresponding to the direction along which the pins are aligned with each other . a series of detents ( not shown in fig1 ) formed on the back of the housing 10 cooperates with a fixed protrusion to enable the user to select an angular position of the light source from a plurality of available positions . as shown in exploded view in fig2 , the vas shroud 12 has a central opening 24 for receiving a quick - release night vision goggle plate ( nvg plate ) 26 . this plate has a fixed upper tab 28 and a lower tab 30 that can be retracted by operation of a release push - button 32 . the tabs 28 and 30 respectively engage upper and lower parts of the shroud 12 to secure the plate to the shroud . an adapter 34 is secured to the quick release plate by a pair of screws 36 , which extend through holes 38 in the adapter and slots 40 in plate 26 , and are threaded into t - nuts 42 located in recesses ( not shown ) in plate 26 behind slots 40 . at the bottom of the adapter 34 are formed two aligned , downwardly open , slots on opposite sides of a gap 44 . slot 46 , which is one of the two downwardly open slots , is formed in part 48 on one side of the gap 44 , and the other slot , which is similar to slot 46 is formed in part 50 on the opposite side of the gap . the slots are aligned with each other . the upper part of the adapter 34 has an opening 52 defined between a rear laterally extending rib 54 and a front laterally extending rib 56 . as will be apparent from fig2 , the downwardly open slots are located on opposite sides of a location below rear rib 54 . a unitary , resilient , clip 58 comprises a horizontally extending element 60 and a vertical element 62 extending upward from the horizontally extending element at an intermediate location between the opposite ends of the horizontal element . the horizontally extending element has ears 64 and 66 extending perpendicularly in a forward direction from its respective opposite ends . the ears are formed with holes for receiving pins formed on the opposite sides of the back cover 68 of the light source housing . thus , pin 22 fits into hole 70 in ear 66 , and the other pin ( not shown ) fits into a similar hole 72 in ear 64 . the horizontal element also has a pair of tabs 74 and 76 extending upwardly therefrom on opposite sides of the vertical element 62 . the vertical element has a rearwardly extending part 78 at its upper end . the upper surface of part 78 is preferably slightly concave so that it can be firmly engaged by a user &# 39 ; s thumb or finger , and may be formed with serrations for increased friction when engaged manually by a person &# 39 ; s thumb or finger . a downwardly open slot 80 is formed underneath the rearwardly extending part . an assembly consisting of the light source housing 10 ( fig1 ) and the clip 58 can be quickly attached to the adapter 34 , which will already have been secured to the nvg plate 26 , by inserting tabs 74 and 76 into slot 46 and the similar slot in part 50 while passing the upper part of the vertical element 62 upward through gap 44 and opening 52 in adapter 34 , and pushing the upper portion of vertical part 62 rearward until part 78 snaps over rear rib 54 and rear rib 54 is engaged with downwardly open slot 80 in part 78 . the assembly consisting of the light source housing and the clip can be removed from the adapter by pressing forward on the inclined surface on the upper side of part 78 to disengage slot 80 from rib 54 . as shown in fig2 , nvg plate 26 has a set of teeth 82 which can be selectively engaged by complementary ribs on a night vision goggle assembly for adjustment of the height of the goggles . a similar adjustment of the height of the light source housing is less critical but nevertheless possible , and the adapter 34 is provided with a set of teeth for engagement with teeth 82 on plate 26 . the light source can be mounted on the vas shroud when the shroud is not being used to support night vision goggles . the light source can be attached and removed in either of two ways . it can be attached and removed by manipulating the clip 58 to attach and remove the assembly consisting of the clip and the light source housing to and from the adapter 34 . alternatively , the assembly consisting of the light source housing , the clip , the adapter and the nvg plate can be attached to and removed form the shroud 12 by manipulation of push button 32 . the use of the clip provides for convenient transfer of the assembly consisting of the light source housing and the clip from the adapter 34 to an alternative adapter 84 as shown in fig3 . adapter 84 is preferably a unitary molded device having a construction similar to that of adapter 34 . two aligned , downwardly open , slots are provided on opposite sides of a gap 86 . one such slot , 88 , is formed in an part 90 , and the other slot ( not shown but similar to slot 88 ) is formed in part 92 on the opposite side of the gap . the slots are aligned with each other . the upper part of the adapter 84 has an opening 94 defined between a rear , laterally extending , rib 96 and a front laterally extending rib 98 . the downwardly open slots are located on opposite sides of a location below rear rib 96 . t - shaped slots 100 and 102 are provided in flanges 104 and 106 respectively to receive a headstrap ( not shown ), which can be an adjustable strap woven from a stretchable yarn . fig4 and 5 illustrate the attachment of the clip 58 to adapter 84 . as in the case of adapter 34 , the clip 58 , with the light source housing attached to it , can be attached to adapter 84 by insertion of the upper end of its vertical part 62 upward through opening 94 while at the same time inserting its tabs 74 and 76 into the downwardly open slots in parts 90 and 92 , and then pushing part 78 so that its downwardly facing slot 80 receives rib 96 . the clip can be removed from adapter 84 by pressing forward on the upper part 78 of the clip . as shown in fig5 , the rib 96 is configured so that the part thereof that enters slot 80 underneath part 78 of the clip is located slightly forward of the back face 108 of the adapter 84 . this configuration of the rib allows the clip to engage the rib without the tip of part 78 pressing into the user &# 39 ; s forehead . as shown in fig5 , the back cover 68 of the light source housing is provided with a series of detents 110 arranged on an arcuate portion of the back cover centered on the connecting pins ( not shown ) on which the light source housing is pivoted . these detents cooperate with a protrusion 112 formed on the clip 62 to hold the light source housing at any selected one of several discrete angles . from the foregoing , it will be seen that the clip allows the light source housing to be transferred quickly and easily from one adapter to the other so that it can be mounted on the nvg shroud on a helmet or alternatively on a similar to the headstrap of a conventional personal headlamp . in the third embodiment , shown in fig6 - 8 , the lighting device is mounted for tilting up and down by engagement of a ring formed at one end of the lighting device with a bracket in the form of a collar extending forward from a clip . the lighting device is similar to the lighting device shown and described in u . s . pat . no . 7 , 568 , 812 , granted aug . 5 , 2009 . the disclosure of u . s . pat . no . 7 , 568 , 812 , is here incorporated by reference . as shown in fig6 , the lighting device 114 includes a light source housing 116 for containing light emitting diodes , power supply cells , and control circuitry , a lens 118 , through which light from one or more light emitting diodes ( not shown ) is emitted , an operating push - button 120 located on top of the housing 118 , and a mounting ring 122 extending from one end of the housing for rotation in a ring - shaped bracket 124 , which is secured to , and extends forward from , a clip 126 . a series of notches 128 is provided on the outside of the ring 122 for engagement with a resilient protrusion 130 on the clip to hold the light at a selected tilt angle . protrusion 130 extends through a slot 132 in bracket 124 . as in the first embodiment , a pair of upright tabs , including tab 134 , engage downwardly open slots ( not shown ) formed in the bottom of an adapter 136 , which is similar to adapter 34 in the first embodiment . a resilient element 138 , protruding upward from the lower part of clip 126 , can extend through slot 140 in adapter 136 to secure the clip temporarily to the adapter . an end cap 142 closes the opening of ring 122 when the device is fully assembled as shown in fig7 . in order to prevent activation of the lighting device by accidental operation of pushbutton 120 , the device 114 can be tilted upward and held in the upwardly tilted position so that the pushbutton is in a pushbutton - protecting position between the housing 116 and the resilient element 138 of the clip 126 , and therefore prevented from accidental operation by contact with objects such as tree branches , or from accidental operation when packed with other objects in a backpack , for example . as shown in fig8 , detents are provided to lock the light source housing in the pushbutton - protecting position . the internal surface of the ring - shape bracket 124 is formed with an inwardly protruding tab 144 , which enters a gap between two adjacent outwardly protruding tabs 146 and 148 formed on ring 122 when the lighting device is tilted upward to a position in which the push - button is protected . resilience of the ring 128 , or resilience of the tab , allow the tab 144 to engage with and disengage from the gap between tabs 146 and 148 . the individual user can therefore readily tilt the lighting device upward to a position in which the pushbutton is substantially inaccessible , that is either inaccessible or accessible only with difficulty , and the lighting device will be held in that condition by tab 144 until a torque is applied sufficient to break the engagement of tab 144 with the gap between tabs 146 and 148 . the size and relationship of these tabs , and the resilience of the part of the ring 122 adjacent tabs 146 and 148 , can be selected so that the torque required to disengage the tabs is sufficient to prevent accidental rotation of the lighting device out of its pushbutton - protecting position . typically , this torque will be greater than the torque required to adjust the angle of the light by disengaging a notch 128 from protrusion 130 . the lighting device , clip and bracket shown in fig6 can be used with a headstrap adapter similar to the adapters shown in fig3 , 4 and 5 instead of with adapter 136 . numerous modifications can be made to the devices described . for example , the configuration of the clip can be modified to provide for pivoting of the light source housing about a vertical or oblique axis , or for universal adjustment of the direction of the light beam . many other modifications can be made without departing from the scope of the invention as defined by the following claims .