SE508487C2 - Method and device for protective switching in a telecommunication system - Google Patents

Abstract

The present invention relates to a system and a method respectively for protection switching in a communications network such as e.g. a telecommunications network which comprises a number of nodes. Each node comprises a number of signal equipment units (11, ..., 1n) providing access to/from the node. At least one redundant equipment unit (1n+1) is provided and a protection switching arrangement (10) is arranged for protecting signals to/from the equipment units. The switching arrangement (10) comprises a number of first switching means (21, ..., 2n) which connect to the access units (11, ..., 1n) and in said first switching means signal input/output means (31, ..., 3n; 41, ..., 4n) are arranged which provide conversion between external traffic signals and internal traffic signals. At least a number of the first switching means (21, ..., 2n) are connected to at least one second switching means (7) which in turn connects to said at least one redundant equipment unit (1n+1). When protection switching is needed for a signal to/from an equipment unit (11, ..., 1n), protection switching is done on an internal signal in at least two steps via a first switching means and a second switching means to/from a redundant access unit (1n+1).

Description

10 15 20 25 30 508 487 2 In addition, in US-A-5 329 520 it is intended to protect long fixed connections via switching in a cross coupling.

However, none of the systems' equipment units are such devices that provide access to the cross couplings or coupling matrices, etc., protected and a fault or the like in such devices may result in loss of important signals.

BRIEF DESCRIPTION OF THE INVENTION What is needed is therefore a system through which protective switching for equipment units or especially access devices are provided.

What is needed is therefore also a device and a method for providing protection for equipment units or devices that allow access to e.g. switching matrices or cross-connectors, etc., or to provide protection for equipment units or access devices generally in a communication system.

There is a need to also provide protective switching for traffic-carrying parts, etc., for example. must meet high requirements for transmission parameters, for example as long as the heart rate monitor. attenuation, mismatch attenuation impedance, etc. be taken into account and in particular supply no. protection switching for fast electrical signals at the same time as such requirements are met.

What is needed is also a system, a device and a method that provides cn »fun - protective switching, i.e. the time for switching from one device to another in case of malfunction, etc. is short. For a number of applications, the switching time must be xnv. so short that it is not possible to use, for example, electromagnetic relays.

What is needed is also a cost-effective protection switching in a communication site; In addition, a system / method, etc. is needed which satisfactorily provides protective switching of signals which are sensitive to switching, i.e. without being harmful affect the signals so that relevant parameters are destroyed or negatively affected to an unacceptable clcl degree.

Therefore, a system / device is provided through which external signals are converted to internal signals, which can be switched from an equipment unit or the like, such as can not 10 15 20 25 30 508 487 3 or should not receive a signal intended for it, to a redundant device. Conveniently the conversion of the converted internal signal takes place in two steps via the first and second coupling means. However, it can also be performed in more than two steps. Advantageously, they include the former the coupling means the conversion device, e.g. input / output devices extensive tennining circuits for extreme fast signals which are to be converted into internal signals such as has a format less sensitive to switches. However, the invention also fits low speed signals, optical signals, microwave signals, etc.

In an advantageous embodiment, the equipment units comprise access units. The system includes in in particular a protective switching arrangement with a number of first coupling means which are connected to the equipment or access units, each first coupling means comprising signal input / output devices. At least a number of the first coupling means are connected to at least one second coupling means, which is connected to the at least one redundant access device. When protection switching is required for a signal to an equipment unit or especially an access unit, the protection switching is performed in two steps via a first coupling means and a second coupling means to a redundant equipment unit.

In an advantageous embodiment, this refers to a communication system in which the extreme signals are high speed electrical signals. However, the invention can also be applied to other signals such as low speed signals, optical signals, microwave signals, etc. The node to which the equipment units or access units are arranged, e.g. include a selector array or a cross coupling. The extreme signals can in particular be high speed signals which must meet the requirements of CCITT (ITU-T) Rec. G.703 standard. Examples of the signals are 155 SDH or 140 PDH Mbps signals, but of course the invention also fits other signals.

In particular, it can also be applied to signals that also have higher speeds, e.g. future systems in which the signal speeds are significantly higher.

In an advantageous embodiment each first coupling means comprises switching devices, e.g. multiplexing and / or demultiplexing devices for coupling between a equipment unit or an access unit and the second coupling means thus provides one first switching step. The connection to and / or from a redundant is made compulsory equipment unit or access unit via the other coupling means to which each or at least a number of first coupling means are connected where the second coupling means through one switching device, e.g. a multiplexing device selects which first coupling means 10 l5 20 25 30 508 487 4 which will connect to the, or a, redundant device and preferably via a demultiplexing switching device selects to which first switching means a signal from a redundant access device will be transmitted. In the case of signals from a redundant equipment unit or access unit, the so-called first connection step takes place in the first the coupling means after the second coupling step has been placed in the second coupling means.

The signal is in the latter case converted from an internal signal to an external signal in the selected one first coupling means. The protection ratio 1: N is given by the second coupling means and according to the present invention is below one, i.e. N is advantageously larger than one. In an advantageous embodiments, N is equal to 15 or 16 where N corresponds to the number of equipment units or access devices for which protective switching is to be arranged. However, the number is equipment units unlimited for the purpose of the present invention. Conveniently the number of first switching means corresponds to the number of equipment units for which protective switching shall be made possible, i.e. a first coupling member for each equipment unit.

In yet another alternative embodiment, the protection switching can be performed in more than two coupling step.

The invention fits regardless of the arranged redundancy or the protective switch the coupling matrix or the cross coupling. For example, it does not need to be protected at all or it can be duplicated or tripled or even more than tripled. Suitable are cables or customer cables, in a special design that carries the extreme signals directly connected to the first the coupling means which comprise input / output device or conversion device for to convert the external signals to internal signals (and from internal to external signals).

The requirements for switching time may be different for different systems and the invention is not limited to a specific handover time.

A protection switching device is also provided, which comprises a number of signaling equipment. or access units, which provide access to / from a selector array or the like. Like one alternatively to a standard access device, e.g. in case of malfunction or similar, can the signals via protection switching means are switched to some other units, e.g. a redundant access device. Input / output devices are arranged in the protection switching device for conversion between external and internal signals. Protective switching takes place on internal signals but especially the extreme signals are signals which are sensitive to changes, e.g. electric high-speed signals and must, for example, meet the requirements of CCITT Rec. G.703 while they 10 15 20 25 30 508 487 5 the internal signals on which a conversion is performed (or from which a conversion is made) are less sensitive to switches. In particular, the protection switching device comprises first and other coupling means and thus provides protective switching in two steps.

The device generally refers to the protection of signals to / from traffic-carrying equipment extensively a number of equipment units such as, for example, access units in a telecommunication system.

In addition, a telecommunication system comprises at least one node, which comprises a selector, for example a cross coupling or a selector matrix (replicated or not) or the like and a number equipment units, e.g. access devices that provide access to / said cross-connection or the like where protection is provided for said equipment or access devices. At least one additional access unit is provided and a protective switching device for connecting signals to / from said redundant access device if a (regular) access device is faulty or off no other reason should be used. The protective switching device comprises signal conversion device for converting between external signals and internal signals less sensitive to switches than said extreme signals. Protective switching takes place on the internet signals.

In particular, the coupling is performed in two steps by first and second coupling means. Suitable is for each access unit first coupling means arranged where said first coupling means comprises said signal convection device for converting an external signal to an internal signal and vice versa. In the first switching means the first switching step takes place in which a selection is cast between a (regular) access unit and a second coupling means. In said other coupling means a choice is made between a number of first coupling means, i.e. from which first coupling means one signal will be transmitted to the redundant access units.

For an extreme signal incoming to a cross-connect or the like, the first is performed the switching stage before the second switching stage while for a signal leaving the cross-coupling via a redundant access unit, the second switching step takes place before the first switching step.

In addition, a method of protecting signals passing through at least one distress comprises one number of surrounding equipment units, e.g. access devices given. The method comprises the steps of: arrange at least one redundant unit of equipment, hereinafter simply referred to as a redundant access device; arranging a protective switching device; if an access device is 10 15 20 25 30 508 487 6 defective or similar, connect signals to said redundant access device. Especially performed one signal conversion from an extreme to an internal signal and vice versa in said switching device, which only switches on an internal signal.

Conveniently, the protection switching is performed in at least two steps. In an advantageous In the exemplary embodiment, the redundant access units comprise a processor which controls it second coupling means. In addition, the second coupling means may order the first switching means to perform a protection switching step, i.e. to change a signal to / from the second coupling means.

One method of protecting the connection of high speed signals in a telecommunication network is also given. The method includes the steps of converting extreme high-speed signals to internal signals, performing a first switching step at a signal that cannot be transmitted to an intended one first equipment unit in which the signal is transmitted to second switching means to which at least a number of first coupling means are connected, performing a second coupling step in said second coupling means, which step comprises selecting the first coupling means which will be allowed for to send a signal to a redundant network device. The selected signal is transmitted then to the redundant equipment unit. Conveniently, the conversion between external and internal signal in the first coupling means. In addition, the second coupling means provides 1st connection where N exceeds l.

It is an advantage of the present invention that protective gear can be provided for signals sensitive to switches, e.g. high speed signals or especially electric high speed signals that must meet high requirements e.g. all the way to pulse shape, mismatch attenuation, impedance, etc. is intended without risking the signal being destroyed or not will meet the given requirements. Another advantage of the invention is that the switching time is short, especially shorter than that which can be achieved using electromagnetic relays.

Another advantage of the invention is that the protective device is reliable and that the availability as such is not reduced or suffers from the clutch. Another advantage is that protective switching is cost-effective and the power dissipation is low.

BRIEF DESCRIPTION OF THE DRAWINGS 10 15 20 25 30 508 487 7 The invention will be further described in the following with reference to the accompanying drawings, in which: FIG. 1 shows a network node without equipment protection, FIG. 2 schematically shows a number of equipment units for which one protective switching device is provided, FIG. 3 shows a block diagram of a second coupling means for a particular embodiment, FIG. 4 shows a block diagram of a first coupling means, FIG. 5 shows a fl fate diagram describing equipment protection switching.

DETAILED DESCRIPTION OF THE INVENTION Fig. 1 shows very schematically a node 100 in a telecommunication network. Node 100 comprises a triple selector array (SM) 20, 20B, 20c to / from which is provided via a number of tenninalaccess devices (TAU) 1 ,, ___, 1N; 1 ',, _, _, 1'N. To the triple selector matrix, fed via terminal access devices electrical high speed signals and also electrical high-speed signals emanate from the node; the signals are denoted only by In and Out respectively.

Redundancy or protective switching is thus provided for the coupling matrix (or eg a digital cross-connect). However, for the node illustrated in Fig. 1, there is no protection at all arranged for tenninal access devices. Examples of tenninal access devices are, for example Station adaptations (ET) in ATM (Asynchronous Transfer Mode Switches) or in The AX system from Ericsson.

However, the node illustrated very schematically in Fig. 1 is an example of a node for which equipment protection (i.e. here protection of tenninal access units) can be arranged according to the invention. Of course, the coupling matrix does not have to be tripled; it can also be duplicated, not protected at all or more than tripled. In addition, the invention relates to others equipment units than tenninal access units or station adaptations.

Fig. 2 shows an embodiment of a protection switching system for protecting a number equipment units 1 ,, ___, lN where the number N of equipment units to be protected can in principle be an arbitrary number. Advantageously, the exemplary embodiment refers to cases when e.g. 15 or 16 equipment units must be protected. In the illustrated embodiment, the equipment units 1 ,, ___, 1N are so called Terminal Access Devices (TAU |, ___, TAUN). An additional or a redundant terminal access unit lN fl is provided, to which a signal can be connected in the event of a fault or the like in one of 10 l5 20 25 30 508 487 8 the access devices to be protected. The illustrated embodiment refers to one telecommunication network in which the electrical linear signal or the external signal must meet the requirements of the G.703 standard, which according to the above is a very demanding standard.

If an external protective switching device were to be placed outside, the terminal access the unit signal the risk of being destroyed to such an extent that the signal no longer meets G.703 the requirements.

The protective switching device 10 according to this embodiment of the invention comprises a number first coupling means 2 ,, _, _, 2N (also referred to as protection units PU), one for each equipment unit 1 ,, ___, lN-, and other coupling means 7 also designated protection switching unit (PSU) 1: N where 1: N is the protection ratio. In the first switching means 21, ___, 2N a first protection switching step is effected while in the second the coupling means 7 a second protection switching step is provided, which will explained in more detail below. "First" and "second" are here taken only as designations since the order of the switching steps depends on the signal direction, i.e. if it is incoming against an access device or the like, the first switching step is performed before the second, but if one signal leaves a redundant access device, the second switching step is performed before the first increased. External signals lle ,, ___, l lm are thus e.g. input signal to the first the protective switching means 21, ___, 2N. In particular, the extreme signals are electrical high speed signals which meet the G.703 requirements. External signals l2,1, __., 12cN are also outputs from the first switching means 2, ___, 2N which will, however, be described later.

The first coupling means 2 ,, ___, 2N each comprise input / output devices 3,, 41; ___, 3N, 4N_ which are also referred to as conversion devices. In the signal input means 3 ,, ___, 3N the corresponding external signals are tennined and converted to internal signals ll, - ,, ___, l 1 ,. Thus converted in the signal input means 3 ,, ___, 3N the extreme signals, which are more sensitive to coupling, to internal signals which better resist coupling. This means that one formate conversion is done to a format that can be better connected. Signal input means 3 ,,> __, 3N therefore includes, e.g. terminating circuits for pulse conversion, impedance conversion, etc. On a similarly, an internal signal l2il, ___, l2¿ is converted to an extreme signal in the signal output means 4 ,, ___, 4N, which extreme signals e.g. meets the G.703 requirements. The dashed line 22 in Fig. 2 indicates schematically the termination of G.703 signals. Thus, when the conversion from an external signal to an internal signal has been performed, a first switching step is performed in a first switching device 5 ,. In this first switching step, a selection is made for a miscellaneous signal between 10 15 20 25 30 508 487 9 an equivalent equipment or access unit l ,, ___, lN and the redundant equipment or access device IM. In the other direction, for an internal signal 12i ,, ___, 12, »is selected in a second switching device 6 ,, ___, 6N of the respective first switching means 2 ,, ___, 2N whether the signal from a "regular" access unit 1 ,, ___, 1N shall be connected or if the signal from the redundant access the INH unit must be connected. The first switching devices 5, ___, 5N comprise here demultiplexers while the other switching devices 6I, __A, 6N comprise multiplexers. The first coupling means are suitably arranged in the connection field for customer cables, ie customer cables are directly connected to it. The first The coupling means are especially also referred to as protective units PU ,, __ V, PUN.

Thus, if a standard access device 1 ,, | __, 1N can be used, ie there are no errors, the the internal signal l l ,, ,, ___, 1li to the intended standard access unit l ,, ___, 1N. If on the other hand the first access unit l, (for example) is faulty or does not control correctly, they take the first the switching devices 51 of the first switching means 2, the position at the dashed one the line and the internal signal lln are coupled to the second coupling means 7. The second the coupling means 7 comprises an input coupling device 8 in the form of a multiplexing device to which signals from the first coupling means can be sent to the the redundant access units 1 lNf, in the event of a malfunction of an access unit.

The second coupling means 7 also comprises an output coupling device 9 in the form of a demultiplexing device connected to the redundant access units lNt, to transmitting signals from that unit to a first switching means 2 ,, __ j, 2N. The other the coupling step is performed in the second coupling means 7 comprising a selection of which of N first switching means which will transmit / receive a signal to / from the redundant equipment units IM. The extreme signals (eg G.703) end as above already in the the first coupling means or in the protection units (PU) which are as close to the customer cables as possible and the protection switching, the first as well as the second step is performed on an internal signal.

Electronic circuits are suitably used for the protection switching of the internal signals. In figure 2 indicates SIS selector interface signals to / from the selector array that can be provided with redundancy in any suitable manner, which, however, is not encompassed by the present invention.

The second coupling means 7, PSU 1: N provides a protection ratio of 1: N, where N can in principle be an arbitrary integer. Preferably, the switching time is less than 10 ms.

The switching overtime depends on fault detection, processors, etc. The protection switch itself 10 15 20 25 30 508 487 10 according to the invention, as a rule, causes almost no delay at all, e.g. a delay in the order of ps. However, the coupling surface can be shorter or even significantly shorter than 10 ms, but also longer, which depends on a number of factors, requirements and needs, etc.

Suitably operate the equipment's protective switching devices in duplex, i.e. it is performed at transmitted and received signals simultaneously. However, recovery is not limited thereto. In addition, the protection relationship can be defined according to the specific requirements of a user.

In a particular embodiment, there is no microprocessor in the second connector (PSU) but the second switching means (PSU) is controlled by a processor at the redundant ones the equipment units, i.e. TAUM. In alternative embodiments, however, the latter may the coupling means PSU is provided with a processor unit or it can also be designed in other ways.

According to one embodiment, however, the processor IM of the redundant access unit is responsible for make decisions. From a software point of view (in a particular embodiment), the second coupling means treated as a distributed part of the redundant access units. In one embodiment there is channels for one-way communication from all equipment or access devices, ie all "active" equipment units such as the TAUzer to the other connector, i.e. the PSU. The protocol is one ON / OFF protocol, which is active when an equipment unit requests protection switching. When protection switch is well requested, the equipment unit sends the protection switch request to the select arrator process by turning off the select array interface SI (see Fig. 2). However, is this is only one way to accomplish it; a number of other options are also possible, which however, will not be further described herein. The protective switch at the first the coupling means are suitably ordered by the second coupling means. In a suitable embodiment, the equipment units or especially the terminal access units can be provided with the ability to turn off the switching interface when there is a request for equipment protection switch. Alternatively, bits can be set in the interfaces. However, is also other alternatives possible. The equipment units can also be responsible for power supply of the the first switching units and can be provided with a hardware alarm channel to the others the coupling means, which, however, relate only to a particular embodiment, power supply can in principle be arranged in any suitable way. In addition, need the protective switch is not arranged for the power supply but this only refers to a suitable one performance.

A redundant tenninal access device can be essentially the same type as a regular or active one terminal access device. Suitably a control channel is intended for the second coupling means, 10 15 20 25 30 508 487 ll which is active only in standby mode. The software can also be so structured that the redundant terminal access devices (or equipment device in general) take protection switching decision, as described above. Conveniently, it is also responsible for controlling the second coupling means. However, this refers only to a particularly advantageous embodiment.

In the following, a detailed description of the second coupling means 7 (PSU) will be given with reference to Fig. 3. The second coupling member 7, hereinafter referred to as protection switching unit PSU, executes protection switching commands. When one protection switching request PS is received from an equipment unit, here TAU, sends PSU 7 via the control part 15 protection commands to the first coupling means, hereinafter referred to as PU. The control part 15 of the PSU 7 also sends loop commands to the first ones coupling means PU as well as PSU start commands. When protective switching is to be performed (see Fig. 4) the signal received from PU to PSU is turned on or activated (A), the loop command (if loops are used) (B) are off and a protection switch command (c) is given. This means that PSU 7 controls the first coupling means by controlling the protection switching function, the loop function and the deactivation / activation of the signal from the first coupling means PU to other coupling means PSU. The second coupling means 7 comprises a number (here 16) of input signal means l3 ,, ___, l3,6 to which signals lli ,, j __, l lm can be fed from the multiplexer 8, which here is a multiplexer 17: 1, which means that there is 17 inputs and l output. The multiplexers can be analog as well as digital. In this case, 1:16 redundancy arranged. There are 17 inputs due to the internal loop functions and thus loop entrance means 13 are also provided. However, the loop function as such is not essential for the protection switch and of course does not need to be included; it refers to only a special design that allows testing, etc. The multiplexing device 8 chooses which one signal input connection to be allowed to transmit a signal (l ln) (via the input port 23) to the redundant terminal access units TAUU. In a similar way, choose yourselves demultiplexer, which is a 1:17 demultiplexer, to which first coupling means an input signal from the redundant terminal access units TAU ”(via an input port 24 and signal recovery means 16) shall be sent. Coupling is made in the demultiplexer 9 and a first coupling means is selected and the signal is transmitted via one of the outputs 14 ,, __ ,, 14,6, where outgoing internal signals are denoted l2il, v __, l2i, ó. In this case, an additional outlet 14L is also provided for the inner loop to the loop input port 13L of the multiplexer 8 (which, however, is not necessary for the invention). Monitoring logic circuits 17 are provided, e.g. to assist in loop signaling and monitoring of the redundant terminal access devices TAU ”. The signal 10 15 20 25 30 508 487 12 looped from TAU "back to TAU". Via the signal recovery circuit 16 line signals in the transmission direction. However, the monitoring logic and the signal generation here only given for illustrative purposes and alternative solutions are also possible or the functions can also be dispensed with.

In one embodiment, even this is not essential for the protection switch as such, it includes the other the coupling means 7 at least one DC / DC converter. In the illustrated embodiment, the PSU responsible for power supply to the first coupling means. However, this is only an example on kra fi feeding; of course, the first coupling means do not have to be fed through the second the coupling means; the feeding can be done in any other suitable way. Thus is the power supply in this case duplicated, which is also advantageous. Normally a PU is fed through its usual TAU, but if this TAU is incorrect or broken, the power supply is taken over by the PSU.

Conveniently, the second coupling means 7 communicates with the redundant access units TAU ”and in addition it receives error messages from all" active "or regular TAUs. The the second coupling means 7 is suitably controlled by a processor of the redundant access the units TAUU. The logic that generates protection switch commands to the PUs is suitably designed so that the most possible error scenario will not put the PUs in gg " protection switching state ", ie no incorrect protection switching is performed on the PU controlling logic is incorrect. In the embodiment shown, it is assumed that the extreme signals are 140 Mbps signals. In that case, the processor at TAU ”16 checks incoming 140 Mbps connections corresponding to e.g. to 32000 phone calls. If this processor "slows down" can all incoming tracks are interrupted and therefore a safe procedure is used when appropriate the processor sends orders to the other switching means. However, this is not part of present invention.

However, the invention of course also fits other signals such as, for example, 155 Mbps signals and signals with other bit rates equally well. In addition, the invention is equally suitable signals other than electrical signals (high speed or low speed) such as microwave signals, optical signals, etc. However, analog parts are optimized for them relevant clock frequencies depending on the bit rate of the signal Fig. 4 schematically shows a block diagram of a first coupling member 2 here designated PU 1.

The PUs are suitably designed for protective switching purposes and each access level requires 10 15 20 25 30 508 487 13 its own PU. The protective switch at each PU is suitably checked by the PSU, as above. IN In the embodiment shown, there are three control signals to each PU from the PSU. However, PU can of course is constructed differently and this is given only as an example. As above is needed no loop to be arranged. PU can e.g. take the shape schematically illustrated in Fig. 2 only comprising two switches, only one signal, e.g. protection switch active or not.

The first signal is called a protection switching command and when this is active, comes the signal transmitted to the G.703 to be transmitted from the TAUW via the PSU instead of from it ordinary TAU. The second control signal refers to the deactivation / activation signal to the PSU. When this is active, the traffic signal was sent from the PU to the PSU. Finally, when the loop command is active, it is sent transmitted the signal to the PSU. When none of the control signals are active, it means the traffic is normal and thus neither protection nor any test is active. If there is one protection command and the signal to the PSU is turned on, protection switching will be performed.

According to one embodiment, the loop command can be active while there is no switching command and no activation signal to the PSU. In this case, the transmitted signal is fed back from an active TAU to PSU. This is a test and it is advantageously allowed in traffic. Another test, which can be conveniently performed in traffic, is monitored by the received line signal at PSU / TAUNH. In this case, the signal to the PSU is in the activation state. Conveniently, however not allowed in traffic to feedback a signal from the PSU back to the PSU. The signal from the PSU is then sent to line. In this case, protection and loop commands are active while the signal to the PSU is off.

In Fig. 4, a received line signal 11, is received at input port 3, by first coupling means PU ,.

If it is assumed that it is a G.703 signal, it is terminated in said input port 3 ,. Signals 11 ,, (d v s the converted internal signal) is sent to TAU ,. If, on the other hand, there is one protection switching command and an activation of the signal to the PSU, the signal is connected via it first switching device 5, also to PSU instead, i.e. it is sent both to TAU, and to PSU. A signal transmitted from a standard TAU can be coupled through the multiplexer 6, to the output port 4, where the conversion to a G.703 signal 12 ,, is performed. If, on the other hand, connected where a protection command and a signal from the PSU, i.e. where a signal is transmitted from the PSU, so the signal is coupled through the multiplexer 6, to the signal output means or the output port 4, for conversion to an extreme transmission signal l2 ,,. A loop multiplexer S, (for test only purpose; not required for protection) is also provided, which is activated in the case of a loop command or a loop command and a protection switch command. This is 10 15 20 25 30 508 487 14 however, not permitted in traffic as described above.

The termination of the external signals in the input and output ports, i.e. the conversion, requires power supply to the first coupling means. As referred to above, this can be done via it second coupling means. In the embodiment shown, + l2V is duplicated, both from a TAU and PSU. Thus, in this case, the PU feed is also protected. + l2V is of course only given for reasons for exemplification and any other value is also possible.

Fig. 5 shows a fl fate diagram with respect to a suitable embodiment. It is assumed that one HW error occurs at TAU ,, 201. HW error is detected 202. Detection information about HW errors are then sent to the PSU 203A and / or to the switching processor (ema) 203B. Conveniently a protection switching is determined by the switching processor (ema), (SP), 205. Then there are two alternative. The first alternative concerns the sending of a protection command to the redundant ones the access units TAUNH, 206. The protection switching command is then processed at TAUNH, 207 and a protection switch command is sent to the PSU control part, 208. From the PSU 203A, however, an protection switch command in an alternative embodiment is sent to the PSU control part, 208. The path via PSU 203A or via 203B thus refers to two different embodiments.

In addition, the redundant TAUW, 209. The second possibility is that it does not exist protection switching command, 206B. This can e.g. be the case if the protection switch is already active for another TAU. Then information is given to the central processor, CP, 207B.

However, when a protection switching command has been issued to the PSU control part, 208, is given a protection switching command (PS) to PU ,, 210. Then the loop command must is deactivated (if such functionality is applied), the protection command is activated and signal to The PSU command is activated.

A protection switch command is also given to MUX / DEMUX at PSU, which includes selection of input / output no. "i", 211.

Protective switching is then performed at PUi, 212 and at PSU, 213. After PS has been performed, which here means that the system is ready to take over the traffic via the redundant TAUNH, 214. TAUNH takes then over the track, 215, and the control processor (CP) of the system is informed, 216. 10 15 20 508 487 15 It is an advantage of the present invention that protection switching of an internal signal can thus performed by electronic circuits which have significantly better long-term reliability than to such as electromagnetic relays. It is also an advantage that 1st protection, where N is greater than 1, provides a minimal redundancy, which means that the extra cost of obtaining a very high availability is comparatively low, as an example less than 10% for 1:16 protection that can compared to more than 100% for 1: 1 protection. In addition, market adjustments can be made for different cables / connectors through very simple modifications in the first coupling means or in the special embodiments described PU, which means that there may be a PU for e.g. each market while racks, backplanes, TAU and TSU tables will be the same for everyone user. Market adaptation is thus easy to handle and very cost-effective. One another advantage is that the demand consumption is low.

Described exemplary embodiments relate in particular to terminal access units, in particular can terminal units, i.e. circuit boards that handle the line signals to / from, for example, a cross-connection protected. However, protective switching for other types of equipment units is the same of course also contemplated by the present invention. Also in other respects can the invention is varied in a number of ways without being removed from the scope of protection of the claims.

Claims (30)

10 15 20 IQ Un 30 508 487 lb Patent claim A system for protection switching in a communication network, preferably a telecommunication network, comprising a number of nodes, each comprising a number of signal titration units (1 I, __, IN; TAUX.X, LAA_N) providing access to / from said nodes, and at least one redundant equipment unit (1NigTAUNfl) and a protection switching device (10) for protecting signals to / from the equipment units, characterized in that the equipment units (1 ,,, _, 1 _ \ -; TAU, _F, _> __ N) comprise a number of first switching means (2, , _V, 2N) connecting to the access units (1I, _Q, 1N; TAUX; X = I_VWN), each comprising signal input / signal output devices (3 ,, __, 3N; 4 |, _ ,, 4N), which effect conversion between extreme traction signals and less sensitive internal traffic signals for connection, and that at least a number of first coupling means (ZDHZN) are connected to at least one second coupling means (7; PSU 1: N) connecting to the at least one redundant equipment unit (1MffAUN fl), so that when sky dds switching is required for a signal to / from an equipment unit (1 ,, g_, l _ (; TAUAm =, _ A_> N) protective switching is performed on an internal signal in at least two steps via one of the first switching means and the second switching means to / from a redundant access unit (TAUW). 2. A system according to claim 1, characterized in that the extreme signals (1 1c1, ___, 1 1cn; 12, 1 ,, __, 12 = n) are high-speed signals. 3. A system according to claim 1, characterized in that the extreme signals are low speed electrical signals, microwave signals or optical signals. System according to claim 1 or 2, characterized in that the signals are electrical signals. System according to one of the preceding claims, characterized in that the node comprises a selector matrix (SM) or a cross-connection. 10 15 20 25 30 508 487 System according to claim 4 or 5, characterized in that the extreme signals must meet the requirements of the standard according to CCITT Rec. 6,703. System according to claim 6, characterized in that the signals are 155 Mbps STM signals. System according to claim 6, characterized in that the signals are 140 Mbps signals. System according to one of the preceding claims, characterized in that each first switching means (2, _, _, 2N; PU, _;, _____ N) comprises a first switching device (5 ,, _ 4_, 5N) and a second switching device (6 ,, __ 4,6N) for coupling to / from an equipment unit or the second coupling means (7), which thus provides a first coupling step. System according to claim 9, characterized in that connection to / from a redundant access unit (1N, TAUN ,,) is provided via the second coupling means (7; PSU 1: N), to which each or at least a number of the first coupling means (PU ,,; X =, _____ N) are connected and thus provide a second coupling step. System according to claim 9, characterized in that the second coupling means (7; PSU) comprises an input coupling device (8) for selecting which first coupling means (2, ___, 2N; PU,) will be connected to the redundant equipment units. (IN ,,; TAUN +,), ie from which first switching means a signal will be transmitted to the redundant unit. System according to any one of the preceding claims, characterized in that the second coupling means (7; PSU) comprises an output coupling device (9) for selecting to which of a number of first coupling means (Z ,, ___, 2N; PUX) as a signal from a redundant access unit (IN, I; TAUN_,) will be transmitted and that the first switching step is performed before converting the internal signal to an external signal. System according to one of the preceding claims, characterized in that the protection ratio (1: N) provided by the second coupling means (PSU 1: N) and corresponding to the number of equipment units to be protected is lower than 1, i.e. N is greater than 1. System according to claim 13, characterized in that N = 15 or 16. System according to one of Claims 4 to 14, characterized in that the switching matrix (SM) is unprotected or duplicated. System according to one of Claims 4 to 14, characterized in that the switching matrix is three times or more than three times. 17. A system according to any one of the preceding claims, characterized in that (customer) cables carrying extreme signals are directly connected to the first coupling means 121 »12NÉPUXÉX = i» e., »-. \ ') ~ System according to one of the preceding claims, characterized in that the switching overtime is lower than approximately 10 ms. Protective switching device (10) for a communication system consisting of at least one node comprising a selector and a number of signal equipment units (1 ,, _ 4_, 1N; TAU ,, _ ", TAUN) 10 15 20 30 508 487 tf; which provide access to / from the selector, characterized in that the protection switching device (10) comprises signal input / signal output devices (3 ,,, __, 3N; 4 ,, ___, 4, \.) which convert an extreme signal to an internal signal less sensitive to the switching and vice versa and that it comprises further switching means (2 ,, _ N, 2, \ _-, 7) for switching signals to / from a redundant equipment unit (1, \ ._ ,; TAUN ,,) in case a signal cannot or would be sent to a standard equipment unit (1 ,, __ 4,1 _ \ »; TAU ,,, _ A, TAUN) and that the protection switching is only done on internal signals. Protective switching device according to Claim 19, characterized in that from the fact that at least some of the external signals (11 l = ,, __ 4.1 1, \; 12c ,, _ ,, 12c_ \.) are high-speed electrical signals and that the signals are converted in the input / output devices to: xtr- internal signals (1 l ,,, ___, 1 1i; 12¿ ,, _, _, 12,). Protective switching device according to Claim 19 or 20, characterized in: in that the protective coupling device comprises first and second coupling means (2, .I - thus provides protective switching in two steps. Protective switching device according to Claim 21, characterized in: from the fact that in the first switching stage a signal is connected to / from a standard equipment unit (1I, V __, IN; TAU ,, ___, TAUN) if such an approach is used, otherwise to / from the second switching point (. 7) - Protective switching device according to claim 22, characterized in that in the second switching means (7; PSU) which of a number of first switching means will be connected to the redundant equipment units (1N fl ffAUß- fl) and that the number of First switching means corresponds to the number of equipment units. Device according to claim 23, characterized in that 50; C-1 that the second coupling means (7; PSU) is connected to each of the first coupling means (2,, HV, 2 _ \ -; PU ,, __ ,, PUN) and to a redundant equipment unit (lNnffAUx fl). Method for protecting external signals incoming to a number of network equipment, providing access to a selector in a communication network comprising the steps of: - converting the external signals to internal signals, which are less sensitive to switching, - performing a first switching step if a signal can not be transmitted to a intended first equipment unit, in which the signal is transmitted to second coupling means to which at least a given number of the first coupling means are connected, - perform a second coupling step in the second coupling means, which step comprises coupling the signal to a redundant equipment unit, and - transmitting the selected signal to the redundant equipment units. Method according to claim 25, characterized in that conversion between external and internal signals is made in the first coupling means. Method according to claim 25 or 26, characterized in that the second coupling means provides 1: N coupling, where N exceeds or exceeds the number of equipment units. A method for protecting signals conducted through at least one node in a communication system, said node comprising a central switching arrangement and ct: .ir equipment units, the method comprising the steps of: - arranging at least one redundant unit to / from which signals are transmitted min: cr, equipment unit can not / should not be used, - arrange a protection switching device, - if an equipment unit is defective, connect the signals via said redundant unit where the number of equipment units is greater than the number of redundant units, and - perform a signal conversion from an external signal to an internal signal or vice versa before / after the protection switch. 10 508 487 LU A telecommunication system comprising at least one node, comprising a central selector (SM) and a number of equipment units, which provide access to / from the central selector, characterized in that for at least a number of nodes is at least one redundant equipment unit (lwgTAUx-q) and an equipment protection device arranged and that the protection device comprises signal input / signal output devices (3 ,, __, 3N; 4 ,, __, 4N) which effect conversion between external / internal signals, which internal signals are less sensitive to switching and that said protection device further comprises first and second coupling means (2 ,, _ ,, 2N; 7) for coupling signals to / from the redundant equipment unit (1N ,,; TAU> \ -_,), coupling being performed only on internal signals. Telecommunication system according to claim 29, characterized in that the signal input / signal output devices (3l, ___, 3N; 4,, A_4,4 _ \ -) are arranged in the first switching means (2,, gg_, 2, \ i), i which a signal is connected to / from an equipment unit _ (1 l, __ p, l_ \ v, TAU1, __, TAU _ \ -) or the second switching means (7), in which the signal is connected to / from the redundant equipment unit (lgagTAUg-H ).