A first adapter arrangement includes a housing having a sealing end supporting the housing in a vertical wall opening of a casing containing an electronics device, and a connecting end extending externally of the casing for connection with the housing of a companion adapter arrangement. A pair of resilient generally-annular longitudinally-spaced seal members are mounted concentrically about the adapter housing sealing portion for sealing the space between the adapter housing outer surface and the adjacent surface of the casing wall opening. An electrical connector mounted in a through passage contained in the adapter housing includes a conductor contact end connected with the conductors of the electrical device, and a connector contact end adapted for connection with the corresponding contacts of a companion second adapter arrangement. A fastening device serves to connect together the adjacent ends of the adapter housings of the first and second arrangements.