Modular electrical plug and socket connectors

An electrical connector unit adapted to be assembled with at least one further such unit to form a multi-pole electrical plug-and-socket connector block, which unit comprises

• (a) an insulating housing;
• and
• (b) electrical contact means in said housing defining a predetermined direction of making a plug-and-socket connection;
• (c) said housing having a coupling region for mechanically coupling said housing to adjacent units, said housing having at least in said coupling region a rectangular cross section transverse to said predetermined direction, whereby said region has a first pair of opposite external faces and a second pair of opposite external faces, said first pair consisting of a first face provided with a first coupling groove having its longitudinal axis extending in said predetermined direction and a second face provided with a first coupling tongue having its longitudinal axis extending in said predetermined direction and adapted to couple with a said first coupling groove of an adjacent unit by relative sliding movement of said units parallel to said predetermined direction, and said second pair of faces consisting of a third face provided with a second coupling groove having its longitudinal axis extending transversely to said predetermined direction and a fourth face provided with a second coupling tongue having its longitudinal axis extending transversely to said predetermined direction and adapted to couple with a said second coupling groove of an adjacent unit by relative sliding movement of said units transversely to said predetermined direction parallel to said third and fourth faces thereof.