the junction between adjacent attached beacon modules 12 in line sound modules 14 base module 16 and dome 18 to reduce the ingress of environmental contamination when the modules are connected referring still to fig1 each of the beacon modules 12 and in line sound modules 14 may provide a housing 32 for example constructed of electrically insulating thermoplastic in the following example where the in line sound module 14 also provides for beacon functionality the housings 32 of both of the beacon modules 12 and in line sound modules 14 will be of transparent possibly tinted thermoplastic to allow the passage of light it will be understood that when an in line sound module 14 does not include a lamp an opaque thermoplastic material may be employed the housings 32 may generally present a cylindrical periphery in diameter consistent among the modules standard diameters for stack lights 10 include 30 mm 40 mm 50 mm 60 mm 70 mm and 100 mm the depicted lowermost beacon module 12 b may receive from the base module 16 a common voltage along common conductor 34 and multiple signal conductors 35 the conductors may be received through lowermost connector 26 b when joined with connector 26 a in this regard electrical connectors 26 a and 26 b for example may be male and female versions of the same connector to be mechanically inter engageable or may be identical connectors reoriented as in the case of.