Patent GB-1364264-A (GB)
Title: Transmission system including a monitoring system
IPC: H04B17/40
Filed: 1971-10-22
Abstract: 1364264 Supervising repeaters SOC ITALIANA TELECOMUNICAZIONI SIEMENS SpA 22 Oct 1971 [16 Nov 1970] 49198/71 Heading H4L To check the functioning of each group of outgoing and incoming P.C.M. repeaters g1,1 to gn, m a control unit K first selects each group with a respective pulse train address signal. A processing unit C1 to Cn at each station detects the address for its associated outgoing or incoming group and derives its power supply from circuits d1,1 to dn,m which only cease to provide outputs when a malfunction occurs in the associated repeater. This is then detected at K during a reply period which follows the address period and is defined by a reply control pulse sent from K. The interrogation and reply-analysis unit K plugs in to one of the terminal or repeater stations, and consists of a gate E<SP>1</SP> 1  (Fig. 2, not shown) which passes a controlled number of clock pulses through a NOR gate (01) to a transceiver (T1/R1) whose output (γ1 or γ5, Fig. 3, not shown) drives the service line. The number of pulses, which identifies the station to be interrogated, is counted by a counter (CON 1) to a value set manually (at S), whereupon a decoder (DEC) resets another counter (GEN), whose output (I) then blocks gate (E<SP>1</SP> 1 ) and enables gate E1 for a further number of pulses (#), determined by GEN, which thereby sets the period (#1) between the end of one identifying pulse train (γ1 or γ5) and the beginning of the next. The reply control pulse of duration (#2) is generated at the end of each identifying pulse train by a timing circuit (Á1), and fed (via NOR 01) to the transceiver (T1/R1). A pulse received (by T1/R1 in #2 time) to indicate correct functioning of the interrogated station is fed to a reply indicator unit (R/R) which is enabled by a monostable (Á2) triggered by the decoder (DEC) output, for a period encompassing the #2 period. The unit (R/R, Fig. 8, not shown) has a gate (P1) enabled by the monostable (Á2) to permit the reply pulse to change over a bi-stable and turn on and off the lamps (L1, L) respectively; absence of a reply pulse, indicating malfunction, leaves L1 off and L on. The transceiver (T1/R1) consists of three transistors (Fig. 7, not shown) of which one (tr3) transmits the interrogate pulses (at b1) to the service line (l1) through a diode (d2); and another (tr2) is enabled by conduction of the third when a positive potential is applied (at b1) to conduct the reply pulse from the service line (l1) to a second terminal (b2). The devices d1,1 to dn,m which detect malfunction of the repeaters g1,1 to gn,m consist of a transformer (Esr, Figs. 4, 9, not shown) driving a circuit (H) which supplies a pulse to a pulse widening circuit (Al) when an extra or a missing pulse occurs in the P.C.M. line, and a pulse to an integrator I 2  when no pulses occur on the P.C.M. line. An integrator I 3  gives a predetermined output when that number of pulses from the pulse widening circuit (Al) occurs which indicates a predetermined error rate in the P.C.M. signal, and either of the integrators energizes an OR gate (0 2 ) to inhibit a flip-flop (# 2 ) controlled by an oscillator (OSC). The outputs (t J,S , # J,S ) of an A.C.-D.C. converter then go from a D.C. level indicating normal P.C.M. conditions to zero, indicating a malfunction. The D.C. levels pass to AND gates (E2, E3, Fig. 4, not shown) in the processing unit C1, respectively enabled by decoders (DC1, DC2) which respond to a counter (CON2) receiving the identifying pulse trains to test one half or the other half respectively of the repeaters. A monostable (M1) responds if all inputs to the enabled AND gate are high, and generates the reply pulse indicating correct functioning.