Abstract: An apparatus and method for testing for faults in an analog-to-digital (A/D) section and a digital-to-analog (D/A) section of a code converter in a digital time division, multiplex telecommunications system are disclosed. The A/D section is tested by connecting a digital test pattern via the switching network to the D/A section and monitoring for faults by comparing the resulting output to a reference value. The A/D section is tested by interconnecting the A/D section to be tested between a first previously tested D/A section and a second previously tested D/A section and then connecting the digital test pattern to the first D/A section while monitoring the output of the second D/A section for faults.

Abstract: Apparatus and methods for testing digital tone generators in a digital time division, multiplex telecommunications switching system. The tone generator produces both continuous and interrupted tones, and testing of any tone is accomplished by determining if its successive PCM words are stuck-at-dc. (SDD) and if it is an idle tone (ITD). The combinations of ITD and SDD determine whether (i) the tone generator being tested is malfunctioning, (ii) the test method or apparatus itself has failed, or (iii) the tone generator is functioning properly.

Abstract: A method and means for providing a remote data station with access to the program memory of a stored program common control telecommunications switching system. The control complex has an input/output port and a modem for interfacing that port with its switching network. The control has the capability of setting up connections in the network between the modem and a selected trunk. Incoming connections to the modem are given only limited access to the stored program control, that access for the purpose of analyzing incoming data to detect a predetermined code. In the event the predetermined code is detected, the incoming connection is taken down, and an outgoing connection established to a distant station by dialing the number of an authorized station which is stored in the program memory. Full access to the program memory is then allowed, such that full access is provided only to stations whose telephone numbers are stored in the memory of the switching exchange.

Abstract: An idle channel test is provided for a digital time division multiplex and time switching network telecommunications system to detect and diagnose faults in an information path which routes digital information in dedicated channel time slots to and from a "time" switching network. In order to detect and diagnose faults in the information path which includes multiplex/demultiplex circuitry, an idle channel is selected as a test channel at the input to the multiplexer which in turn is the input to the switching network, a test pattern including a bit pattern and a parity bit is inserted into the test channel, the test pattern is connected via the switching network back to one of the demultiplexers and the bit pattern and parity bit are monitored for errors.

Abstract: In a telecommunications switching system having an "all time" network, the network is divided into a plurality of blocks, each of the blocks having assigned thereto dedicated groups of access ports for completing connections between those ports and any of the other ports in the system. A single spare network block is provided having a programmable identity and capable of functioning in the place of any of the primary blocks. In the event of a malfunction in a primary block, the spare network block is assigned the identity of the primary block, is enabled, the faulty block disabled, and call processing continues just as if the primary block were on line.