The present invention teaches a modular telephone jack "system" capable of voice and data applications, which may be relatively flush-mounted within a conventional electrical box or to a surface and which is characterized by the absence of conventional screw terminal technology. A lacing strain relief system facilitates connections in terminal clips which face forward and which are accessible from the front of the system for testing and repair through a snap-off face or cover plate, and facilitates relatively rapid installation and easy access for testing, troubleshooting and wiring. The system may be equipped with combinations of duplex modular jacks of similar outer configuration, such as four, six and eight-conductor versions. The system includes its own "universal" surface-mounting housing or box, where needed.