Patent GB-1268819-A (GB)
Title: Improvements in or relating to control equipment for a transmission network of the "working reserve" type
IPC: H04B1/74
Filed: 1969-05-15
Abstract: 1,268,819. Radio signalling. SOC. ITALIANA TELECOMMUNICAZIONI SIEMENS S.p.A. 15 May, 1969 [15 May, 1968], No. 24863/69. Heading H4L. In a communication system having a plurality of working channels and two reserve channels, means are provided for replacing a working channel, when it fails or becomes degraded, with a reserve channel, each of the working channels having a preferred reserve channel but means being provided to utilize the other reserve channel if the preferred reserve channel is not available. General description. Fig. 1.-As shown, there are six working channels CT1 to CT6 and two reserve channels 1‹R and 2‹R, the transmission side of a section being provided with control equipment Tr and the receiving side having control equipment Ric. Control units R1 to R6 and R7, R8 monitor the working and reserve channels respectively, each unit producing one of three signals indicating that the associated channel is efficient, degraded or failed. A signal A, peculiar to each working channel, indicates that a channel has failed and similarly, a signal D indicates that a channel is degraded, A7, D7, A8, D8 representing these conditions for the reserve channels. Signals A and D are supplied to a decision unit K and if it decides to replace a working channel m a request signal is sent to the control equipment Tr. This signal is #G 1m  if the first reserve channel 1‹R is selected and is #G 2m  if the second reserve channel is chosen. Assuming that the first reserve channel is chosen, the signal #G 1m  is transmitted via T c1  and receiver R c1  to a processor E t1  which compares this signal with signals A‹, D‹, or Q<SP>00</SP> indicating which, if any, of the preceding working channels have failed, are degraded, and which switching operations have been performed on the reserve channels of the preceding section, respectively. This is to ensure that no switching operations occur if the failure is in a preceding section. If the comparison shows that there is no fault in the preceding section, switching unit B t1  replaces the working channel with a reserve channel and a signal F 1  is transmitted back via FT1 and receiver FR1 to the unit K. In the meantime the unit K has generated a signal #P 1m  to initiate the first stage of connecting the working channel to be replaced to a cross-bar B1 and when the signal F 1  is received this switching is completed and the signal Q<SP>0</SP> m  and also signals A and D are transmitted to the next section. The operation is similar when reserve channel 2‹R is selected, the signal G 2  being transmitted via TC2 &c. and cross-bar B2 being used. Details of unit K, Fig. 2.-Unit K comprises a decision unit K11 to K16 for each working channel which co-operates with the reserve channel 1‹R and a decision unit K21 to K26 for each working channel co-operating with the reserve channel 2<SP>0</SP>R, the failure and degradation signals A1 to A6 and D1 to D6 being supplied to the appropriate decision units and also to units CO1 to CO6. An interblock unit Ib 1  receives signals X 1  and Y 1  from decision units K11 to K16, respectively. The signal #Y 1m  indicates that the reserve channel 1‹R has been engaged by a channel m because unit K1 m  has received a degradation signal D m  and this signal Y1 m  causes unit Ib1 to transmit signals a 1  to the remaining decision units K1 to K16 to prevent channel 1‹R being assigned to any other working channel associated with a degradation signal. If the decision unit K1 m  receives the failure signal A m  that unit engages the channel 1‹R and transmits the signal X1 m  to the unit Ib1 and Ib1 transmits the signal b 1  to the remaining units K11 to K16 to prevent the channel 1<SP>0</SP>R being assigned to any other channel associated with a degradation signal or a failure signal. The unit Ib2 operates similarly for the second reserve channel 2‹R, receiving signals X 2 , Y 2  and transmitting signals a 2 , b 2 . The decision units are numbered in order of priority and when a unit K1 m  engages the reserve channel 1‹R on the reception of signal D m  it transmits a signal W1 m  to the decision units of higher number to prevent the same reserve channel being engaged on the reception of simultaneous degradation signals by the units. Similarly, when a unit K1 m  receives a failure signal A m  it sends a signal Q1 m  to all the decision units of higher number. Decision units K21 to K26 likewise generate signals W21 to W26 and Q21 to Q26 under these conditions. NOR gates n1 to n6 generate the signals Q 0  transmitted to the next section to indicate the channels which have been replaced by reserve channels. For example, NOR gate nm will receive signal Q1 m  or Q2 m  from the associated units K1 m , K2 m  respectively. Units CO1 to CO6 are responsive to signals G1, G2 to detect the condition that one or more channels require to be replaced by the first or second reserve channel and that this requirement cannot be satisfied. When this condition is detected for channel m the unit Corn produces either signal B1 m  or B2 m  and stops the request signal G1 m  or G2 m  produced by the unit K1 m  or K2 m . Signals B1 m , B2 m  are stored in the unit Co m  and reset to zero if the signals D m  or Am cease. A clock pulse S periodically tests if the reserve channel has become available and resets signals B1 m  or B2 m  if this occurs and supplies both signals to units K1 m , K2 m  so that if the preferred reserve channel is blocked the other reserve channel may be used. Signals H<SP>0</SP> 1  are provided by unit H 1 , Fig. 1, and comprise the following signals. A signal c1 which indicates the failure or unavailability of reserve channel 1‹R, a signal d1 indicating that channel 1<SP>0</SP>R is degraded, signals E11 to E16 being freezing signals for channels 1 to 6, respectively, and signal Z2, S2 allowing for the engagement of a reserve channel which is not preferred when the preferred reserve channel is not available for various reasons. The signals H‹2 are supplied by unit H2 and comprise a corresponding set of signals. The unit K transmits signals X<SP>0</SP> 1 , Y<SP>0</SP> 1  to unit H 1  denoting that the reserve channel 1<SP>0</SP>R cannot be assigned to a failed or a degraded working channel respectively. Similarly signals X<SP>0</SP> 2 , Y<SP>0</SP> 2  convey the same information to unit H2 regarding channel 2‹R. Signals O 1  are supplied to unit H1 by the units K11 to K16 when these units engage the first reserve channel for a working channel which is of higher priority and unit H1 transmits the freezing signal E1 m  to prevent the switching of the working channel m of lower priority. Similar conditions apply for the second reserve channel, units K21 to K26 transmitting signals O 2  to the unit H2 and unit H2 returning the freezing signal E2 if necessary. The logic circuitry of the units Ib 1 , K11, K21 and Co1 is described in detail. The arrangement is such that a failed channel takes precedence over a degraded channel. Means are also described for selecting manually a working channel for priority over the others.