A master control unit of a cable tester in accordance with the present invention comprises a housing having an upper portion and a lower portion. The master control unit includes a display, a pivotal cover, an indicator, a modular jack, and an activation/selection button. Electronics of the cable tester are disposed with the housing. A remote unit compatible with standard modular jacks comprises a housing for supporting a printed circuit board and a cover. The housing comprises an elongated generally rectangular portion which is sized so as to be compatible with standard modular jacks. During use the master control unit is connected by a jumper cable to a modular jack under test. The modular jack under test is connected by wiring to another modular jack, also under test, at another location. The remote unit is inserted into and mates with the other modular jack. Testing is performed at master control unit. The master control unit includes display indications for low battery and for the presence of line voltage at the display. The switch is used to index through the test modes. The indicator lights each time the button is pushed, with each screen change, during testing, and remains lit to indicate a pass condition.