User selectable overlap and enbloc dialing of ISDN line

An ISDN test set employs a user selectable dialing mechanism, that allows the test set user to select from multiple types of dialing-overlap dialing and enbloc dialing, through the use of a simplified functional dialing key set. The dialing key set, in combination with dialing software employed by the test set's supervisory control processor, provides the user with substantial ISDN dialing flexibility, while reducing interaction between the user/craftsperson and the test set, that minimizes dialing inaccuracies that often depend upon the skill and familiarity of the technician with ISDN communications. Enbloc redialing (of the most recently dialed number) or of a stored number in memory is provided only in ON-HOOK mode by the operation of a REDIAL or RECALL key. Otherwise (whenever OFF-HOOK) only overlap mode dialing is employed.