Patent GB-1045013-A (GB)
Title: Monitoring and control apparatus
IPC: H03K17/82
Filed: 1964-01-08
Abstract: 1,045,013. Automatic exchange systems. WESTERN ELECTRIC CO. Inc. Jan. 8, 1964 [Jan. 9, 1963], No. 842/64. Heading H4K. In an exchange system in which storage devices associated with lines, trunks or similar circuits are periodically scanned, the scanner comprises two similar address matrices of selectable elements, whereby selection, by a central control device, of one of the elements in one of the matrices causes an interrogation signal to be applied to the associated device via a path which includes the corresponding element in the other matrix, the latter element being biased into a low impedance state at this time. The scanner forms part of an electronic control system for a large exchange and almost every equipment in the system is duplicated to ensure continuous working. The scanner thus includes two chains of equipments between the central control device and the monitored circuits and either chain is initially taken into use by central control when it wishes to interrogate a particular circuit. The correct functioning of each equipment of a chain is signalled back to central control during each interrogation, the reverted signals usually being passed through the return paths of both chains whereby a partial testing of the unused channel occurs. Individual equipments and in particular the address matrices can be tested at any time by central control. The two chains of equipments are identified in the drawings by the designations left and right or A and B or 0 and 1, respectively. General description of system.-The devices associated with the monitored circuits are termed " ferrods." These comprise (Fig. 1C) a rod of ferromagnetic material 0000-3115 having a control winding 2001 and 2002 at each end thereof and an interrogate and a read-out winding 2006 and 2008 respectively passing through apertures therein. The control windings are connected to the circuit to be monitored, e.g. the two wires of a subscriber's line. The rod is saturated if current flows in the control windings, e.g. due to a subscriber loop, whereby an interrogate pulse in winding 2006 is not repeated by transformer action to readout winding 2008. The presence or otherwise of a read-out pulse is interpreted appropriately by central control. The circuit diagram of a ferrod is shown in Fig. 1D, the rectifier symbol denoting that the interrogate and read-out windings 2006, 2008 are affected by the control windings but not vice-versa. The ferrods are arranged in a matrix (Fig. 1A). The two wires FOO, FROO of an interrogate loop from the address matrices of the scanner are connected to the interrogate windings 2006 of the first even and odd ferrods respectively of the first row of the matrix. The windings 2006 of the even and odd ferrods of each row are connected in two series chains which are connected together via the primaries of transformers 6ASWT-0 to 6ASWT-31. Similar interrogate loops FOO, FROO are connected to each of the 32 rows of ferrods. The read-out windings 2008 of each column of ferrods are connected in series chains to read-out loops such as ROO, RROO. As was mentioned earlier the scanner comprises two chains of equipments, one of which, for example, comprises a left access unit 1300-1500, left address core matrix 4000-7000 and left output unit 1100-2000. The left or right chain is selected by means of pulses on a left or right input bus EN01 or EN10 (the first digit identifies which chain is concerned). Signals for addressing the cores of the left or right core matrices are applied to either of the access units from " 0 " or " 1 " address buses 0AD00 or 1AD00, i.e. a signal on " 1 " address bus 1AD00 can be applied to either the left or the right access unit depending on which of these units is chosen for the particular interrogation. The cores of each matrix are provided with: row windings, e.g. 41, connected between GO and Return wires by CADO and XAP, which extend to the corresponding access unit, e.g. left; column windings 42 which are similarly connected (not shown); bias windings 44 which are connected in a series loop between bias relay 4A and battery (7R) and interrogate windings 43. Each winding 43 in the left matrix is connected in series with the winding 53 of its corresponding core in the right matrix and the associated interrogate loop FOO, FROO. The bias loops are arranged so that an interrogate pulse induced in winding 43 of core A(0-8) say, by selective energization of its row and column windings has no effect on, and is unaffected by, core B(0-8), i.e. the latter is in a low impedance state. If the bias supply is broken for any reason relay 4A (or 5A) releases and brings in an auxiliary bias supply (4EBR) utilizing the row windings 41 and the fault is signalled to a master scanner over the bus MJ to FA. The master scanner is analogous to the presently described line scanner. The reverse magnetization of the cores under auxiliary bias does not affect the low impedance nature of the cores when the other matrix is addressed. Transistor circuits for the various equipments shown in Fig. 1 are described and only a brief outline of the operation of the system is described below. Operation of Scanner.-Central control selects the left access unit, say, by pulsing leads ENO1 (P, N) and the unit responds and acknowledges. The address of the core corresponding to the ferrods to be interrogated is transmitted over one of leads OAD00 (P, N) to 0AD16 (P, N), say. This address is processed in the unit and then signalled out over the relevant row wire CA00 to CA06 (Fig. 1A) and column wire (not shown). If more than one row or column address wire is energized a detector circuit in the access unit responds to the consequent current surge and informs central control accordingly. The selected core, e.g. A(0-8) in the left matrix induces an interrogate pulse into the loop FOO, FROO whereby, in dependence upon the condition of the supervised lines, a pulse or no pulse is induced in the read-out windings of the ferrods of the first row. A pulse indicating correct operation of the interrogate loop is also reverted to central control via transformer 6ASWT-0, wire GOO, and the left answer circuit, left ASW-S output 1900. The results of the interrogation are passed to the left output circuit 1100-2000 which is pre-selected (lead AIR) by the left access unit. The output from circuit 1100- 2000 is transmitted to central control over both the " 0 " and " 1 " answer buses 0AN00 and 1AN00. Further testing of the read-out loop is achieved by addressing the maintenance amplifiers 600 or 601 whereby a pulse is injected into all of the read-out loops via transformers 6MT0 to 6MT15 whereby the output circuits 1100-2000 and 900-1700 respond as before. The access units also provide timed pulses directly via wires UK1A, UK1B and indirectly via wires SSA and SSB whereby lack of synchronism between these pulses and information pulses applied to the output units initiates an alarm. In general fault conditions caused by break-down of power supplies, e.g. the bias loops, or by short-circuiting of transistors are indicated at central control by blown fuses. The address and control buses between central control and the peripheral equipments, e.g. the scanner, take the form of balanced transmission lines.