A connecting block (24, 26, 28) has printed wiring circuit boards (71, 74) to interconnect terminals with jacks and terminals. The connecting block has a pedestal (32), which sits on a lower crossarm (34) of a frame (10, 12, 14) and a resilient tang (36) which snaps into an upper crossarm (38) of the frame. The connecting block (24) is suspended to expose the terminals (58, 60. 62, 64, 66, 68, 70, 72) to which conductors (11, 13, 15) are terminated. Each circuit board (71, 74) has two near end and far end contact areas forming a plug. The tip and ring conductors in a test cord are connected, respectively, with the two near end contact areas. A keeper spring connected to ground potential retains the plug within a jack having two long electrical contacts for the far end contact areas and two short electrical contacts for the near end contact areas. A tracing lamp will flicker for a predetermined period when the plug is inserted within a jack.