Multiplex communications – Diagnostic testing
Reexamination Certificate
1997-12-03
2001-07-03
Jung, Min (Department: 2663)
Multiplex communications
Diagnostic testing
C370S524000, C379S021000, C379S209010
Reexamination Certificate
active
06256294
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to telecommunication systems, and is particularly directed to a user selectable dialing mechanism, that is incorporated within a craftsperson's test set having an architecture of the type described in the above-referenced '117 application, for facilitating the operation of the test set and thereby testing of an ISDN communication circuit.
BACKGROUND OF THE INVENTION
As described in the above-referenced '117 application, a variety of telecommunication test units have been proposed for testing various types of digital signalling circuits. Such circuits may include, but are not limited to, those transporting high-bit-date digital subscriber-line (HDSL) signals, asymmetric digital subscriber line (ADSL) signals, digital data service (DDS) signals and integrated services digital network (ISDN) signals. Unfortunately, such conventional test units are relatively cumbersome and hardware-intensive devices, typically resident in a telcom service office or other fixed system installation, that affords only a single point of access to the circuit of interest.
A non-limiting example of such a conventional test unit is described in the U.S. Pat. No. 5,208,846, to Hammond et al, entitled: “Subscriber Loop Tester for Telephone Switching Systems.” In order to be connectable with various types of telecommunication circuits, the Hammond et al test unit contains different types of line interfaces/jacks. Determining which jack is to be used requires that the test system operator have a prior knowledge of the communication link to which the test set is to be coupled. Without this knowledge, the user does not know to which jack the line should be connected, and cannot readily configure the test unit to support a particular user interface and associated termination hardware.
As noted above, conventional test units are relatively large and fixed pieces of equipment, so that they are not readily suited for use in the field (i.e., they are not portable), so that they cannot be readily interfaced with any accessible location along a communication link. This relatively poor facility of transport and ready connection to any location along a link to be tested also limits the practicality and effectiveness of such test units.
These shortcomings have become a particular concern to telecommunication service providers, especially with the continuing expansion and demand for integrated services digital network (ISDN) services. Not only is there currently a need for a practical, portable test set that is capable of testing already installed ISDN circuits, but one which can perform ‘dry loop’ line testing, prior to its use for ISDN service; namely, there is a need for an ISDN test device that will permit a circuit to be ‘prequalified’ (as ISDN-capable), before ISDN equipment is purchased and connected to the line to be used for ISDN service.
Advantageously, the portable test set described in the above-referenced '117 application contains a communication architecture that is readily interfaced with virtually any location along a line/circuit to be tested, so as to allow testing of the line, irrespective of its configuration (e.g., two-wire vs. four-wire), or the type of signals that may be conveyed over the line (analog or digital). In addition to circuitry for testing the operation of a standard analog (POTS) line, the portable test set described in the '117 application contains a digital communications controller and associated digital signalling interface circuits, including both ‘U’ interface and ‘S/T’ interface circuits.
Thus, the test set can be interfaced with either a two-wire network link or a four-wire customer premises link, and may transmit and receive ISDN bearer channel messages over whatever line to which it is connected. The contents of such bearer channel messages may be defined to evoke prescribed responses from a companion test set coupled to another portion (relatively far end) of the communication circuit of interest, so that the line linking the two test sets may be tested. When two such test sets are interfaced with spaced apart locations of the circuit/line under test, they may operate in respective master and slave modes, allowing a craftsperson using the master test set to initiate a bit error rate test (BERT) from one end of the circuit, and derive a measure of the operational performance characteristic of the in-between segment of the circuit.
SUMMARY OF THE INVENTION
The present invention is directed to an enhancement of the ISDN communication and testing capability of the test set described in the '117 application, that allows the test set user to readily select either overlap mode dialing or enbloc mode dialing, through the use of a simplified functional dialing key set. Enbloc speed redialing of the most recently dialed number is provided only in ON-HOOK mode by the operation of the REDIAL or RECALL function keys. Otherwise (whenever OFF-HOOK) only overlap mode dialing is employed. This 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.
As in the case of a conventional POTS telephone, overlap or sequential DTMF dialing involves the transmission of the individual digits of a dialed telephone number—one digit at the time. In a standard analog POTS dialing scheme, using dual tone multifrequency (DTMF) signaling, as the digits of a called number are keyed-in, DTMF tones associated with the dialed digits are transmitted in sequence, with a digit (tone) on period followed by a quiescent or off period between digits. This tone-on, tone-off sequencing allows the network switching equipment to distinguish between respective tones of a dialed number sequence.
For ISDN signalling, however, instead of being transmitted as in band tones, the digits are transmitted as a sequence of digital (bearer channel) messages, each of which is associated with a respectively dialed number. To initiate the overlap mode of dialing, the user first takes the test set OFF-HOOK by operation of an OFF-HOOK key on the test set keypad. (Whenever the test set is OFF-HOOK, enbloc dialing is blocked.)
Assertion of the OFF-HOOK key causes the dialing routine to transmit an overlap dialing mode call set-up message over the D channel to the public switched telephone network (PSTN). In response to an overlap mode call set-up message (which contains no dialed digit information as does an enbloc call set-up message, to be described), the network switch sends back a call set-up acknowledgement message, and waits for the digits to be sequentially transmitted from the test set, in the form of a cascaded sequence of D channel information messages, each containing the identification of a respective digit.
Since an ISDN call set-up message is a data message, the network switch will not normally return an in-band dial tone signal that would be played back to the user via the test set's speaker. To provide dial tone for the benefit of a POTS-familiar craftsperson, when the call set-up acknowledgement message from the switch is received (and in the expected absence of in-band dial tone signaling) from the network, the overlap dialing routine causes a POTS-type dial tone to be audibly generated via the test set receiver/speaker.
Upon hearing dial tone, the craftsperson knows that he can begin keying in (dialing) the called telephone number. Dialing of numbers can be conducted in one of two ways: 1) memory access speed dialing, where the number is accessed from memory in accordance with a speed dialing format, to be described, or 2) key dialing, where each digit of the dialed number is generated in accordance with user operation of a respective key on the test set keypad. If memory access speed dialing is to employed, the craftsperson operates a RECALL key, which invokes a RECALL subroutine.
When the RECALL subroutine is called up, a list o
Katz Paul H.
Kennedy Michael
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Harris Corporation
Jung Min
LandOfFree
User selectable overlap and enbloc dialing of ISDN line does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with User selectable overlap and enbloc dialing of ISDN line, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and User selectable overlap and enbloc dialing of ISDN line will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2453947