Patent GB-1281454-A (GB)
Title: Telephone calls simulator
IPC: H04M3/32
Filed: 1970-10-22
Abstract: 1281454 Automatic exchange systems INTERNATIONAL STANDARD ELECTRIC CORP 22 Oct 1970 [26 Nov 1969] 50127/70 Heading H4K A program controlled data processor tests the functioning of an exchange by setting up connections between selected pairs of test line appearances on a main distribution frame, the appearances being scanned in order to connect and disconnect test circuits from the test lines as and when necessary during the progress of each connection. So long as at least three test lines are free the processor continues to set up further concurrent test calls to test for dial tone, ringing current, ringing tone, transmission of voice frequency signals and busy tone as well as response of the exchange to off-hook, dialling, reply and release signals. As shown in Fig. 1 the main distribution frame 2 of a switching network 1 has a group of 100 test line appearances 9. Each test line terminates on a circuit 10 with relay contacts 11a to simulate switch hook signals and each line can be connected to a circuit 16 to send multifrequency digits to set up calls, to a circuit 17 to detect ringing current or to a circuit 19 to detect dial, ringing, and busy tones as well as simulated speech tones. A generator 18 is connected to apply simulated speech tone. These test circuits are connected and disconnected by relays 12 to 15 controlled from a distributer 24 comprising an order register 27, a decoder 26, and an address register 25 instructed by the processor 31. So long as an order is registered in 27 the associated relay stays operated. A scanner 29 relays to the processor signals received by test detectors 17 and 19. Manipulation of the test calls and their supervision is effected by cyclic scanning of a store 30 in which each test line has a storage cell. A storage cell of a free test line is detected by a call selection circuit 45 which provides a storage cell 50 with the identities of test lines nominated as to be calling and called in a test. Test particulars in cell 50 cause the cells of the nominated calling and called lines to be marked as calling and called lines and each to indicate the identity of the other line of the pair. Each cell also has a call phase code to indicate the current sequence state of the call, and has a timing code set up appropriately for each test and counted down scan by scan of the store before a test is applied. The timing codes are also used to time the action of multi-frequency voice frequency number sending from circuits 16 and can also be employed to send loop disconnect digit trains by operation of relays 11. When the processor, using scanner 40, finds a storage cell indicating calling status and a phase code #1 it addresses the associated test line to operate relay 11 to simulate off-hook and advances the phase code to #2. At the next scan the processor responds by connecting up receiver 19 to await dial tone, sets a time count in the storage cell and advances the phase to #2.1. Scan by scan the time count is reduced and if, before its expiry, dial tone is received, phase 3 is entered and the receiver 19 is disconnected. The associated line nominated as called line is now identified and its storage cell is marked with phase code #3.1, digits to be dialled being taken one by one from this cell and used to control sender circuit 16 or contacts 11a. The phase of each line cell is advanced from #3.1.1 to #3.1.2 and so on for each digit and timing is effected by appropriate timing codes. When all digits have been sent the phase code in both cells is advanced to #4. The called line cell now causes the processor to connect up the ringing current detector 17 with a time set for receipt. By similar processes a phase #5 supervises the receipt of ringing tone by the calling line, phase #6 simulates reply by the called line, phase #7 detects release of ringing current, phase #8 sends simulated speech tones, phase #9 detects receipt of speech tones, phase #10 detects ending of speech tones, phase #11 detects release by calling line, phase #12 detects busy tone which is connected automatically on release of the calling line, phase #13 detects release of called line, while phase 14 is concerned with registration of test call particulars on a print out device 41. If any of the tests fail to satisfy the timing criteria the lines are released and the storage cells are given a code indicating the nature of the fault so that at a subsequent scan the fault may be recorded on print out device 41. The test circuits 16, 17, 18 and 19 may be provided for each test line as shown in Fig. 1. Alternatively, one set of test circuits may be used on a time shared basis to serve all the lines, Fig. 2, not shown. The selection of pairs of test lines for connection may be made within the processor 31.