An electrical adapter (100) includes a first housing member (1), a second housing member (2) coupled with the first housing member to define an internal space therebetween, and a subassembly (3) received in the space. The first housing member has a first mating face (11) defining a first upper and lower cavities (111, 112). The second housing member has a second mating face (21) defining a second cavity (211). The subassembly includes a first, second and third circuit boards (311, 321, 331), a surge suppressing device (34), a number of first, second and third conductive terminals (312, 322, 332) respectively mounted on the first, second and third circuit boards, and a number of contact vias (35) electrically connecting with corresponding first, second and third terminals. The first, second and third terminals respectively have contacting portions (314, 324, 334) extending into corresponding cavities. The surge suppressing device is mounted on the first circuit boards and electrically connects with corresponding first, second and third terminals for transient voltage protection via the contact vias.