FR2481462A1 - Monitoring system for multiwire telephone cable connections - employs optical detectors selected by gates to provide audible and visible alarms for differentiating between damp and faulty wires - Google Patents

Abstract

The system monitors the connections and particularly the insulation problems due to humidity in multiwire telephone cables. A fault monitoring cabinet is located in a telephone exchange and monitors a number of cables via OR gate selectors controlled from a control unit. The selector outputs are applied to detectors comprising comparators which drive photocouplers. Lamps signal prescence of humidity in partic. cables while an audible alarm signal, that one of the cables is faulty. The photocoupler outputs are gated (54) through monostables to enable a NAND gate in oscillator circuits to drive a loudspeaker. A digital display unit identifies the number of a connection.

Description

- 2481462

- 1 -

TELEPHONE CABLE CONNECTION MONITORING SYSTEM

MULTI-THREAD.

The invention relates to monitoring of rac-

  multi-wire telephone cable cords. It concerns more

particularly an automatic detection and detection system

  risks of insulation faults in cable connections in operation. It further relates to telephone cable section connections allowing the implementation

of the system of the invention.

  We know that in the vast majority of cases, the

  faults affecting the operation of multiple telephone cables

  twisted pair or quarter tifils appear at the sleeve fittings and are insulation faults. In

  systems of the known kind, we directly control the isolation

  on one or more pairs available by means of an equi-

electronic insulation control unit located in a bay

  monitoring. A light or audible alarm signal is

automatically triggered when the insulation resistance to earth of at least one of the monitored wires decreases

  below an alert threshold. In fact, it is best to pre-

see two alert thresholds, the highest of which triggers a

  non-urgent alarm and the lowest an urgent alarm. Voy-

light ants identify the affected pair (s)

  of the fault. Not only do these systems not allow lo-

  precisely pinpoint insulation faults along a

248 1462

  -2- cable, but furthermore they lose Ecu- in: interest due to the

  progressive substitution of so-called "olastic" cables for cables

so-called lead lead.

  In the lead cable, which cc2-: carries paper-insulated wires under a lead sheath, the insulation resistance

  of the monitored pair gradually decreases due to

pours humidity. We can therefore assign the threshold of a-

  non-emergency tear a value high enough to allow an intervention to be triggered before the cable becomes really defective. In the "clastic" cable, in which the insulation of the wires and the sheath are made of polymeric materials, the insulation resistance is not a progressive function

  humidity level. It goes almost instantly from a va-

  their very high to a very low value as soon as moisture enters the connectors of the fittings and the distinction between "urgent" alarm and "non-urgent" alarm no longer makes any sense.

We only cite here for the record the

so-called "echometers" or "reflectometers" which allow to send calibrated pulses in the wires and to analyze

the reflected pulses. These devices are expensive, the in-er-

  preparation of the reflected signals is delicate and above all the pro-

  assigned does not lend itself to automatic control from a

monitoring bay.

  The invention is based on the fact that, for the most part, insulation faults appear in the fittings and are due to the introduction of moisture inside the insulating sleeves, in principle leaktight which

  protect the wire connectors of these fittings.

  A first object of the invention is a system of over-

  permanent and automatic monitoring of multiple telephone cables

  tifils which makes it possible to predict the appearance of an insulation defect

and locate where it should appear. More pre-

sharply, the system of the invention triggers a-

  alert and identification not when an insulation fault appears but when the humidity inside a

  connection sleeve reaches a value such as a notable risk

  ble insulation fault appears. The invention also applies

  both for monitoring plastic cables and for over-

-3-

monitoring of leaded cables.

Another object of the invention is a connector for

  multi-wire telephone cables allowing the application of the system

  teme of the invention and wherein, in addition, the wires and their connectors are better protected from moisture than in the rac-

cords of the known genus.

  The surveillance system of the invention is characteristic

terized in that it includes - inside the protective sleeve of each fitting, a

  humidity detector connected on the one hand between a wire

  determined ve (i.e. a determined thread not assigned to the ex-

  cable), this wire being chosen as a potential reference and being called "bus wire" and on the other hand 1 to n reserve wires called "test wires", said detector causing a drop in contact resistance between the omnibus wire and the test wire or wires when moisture has entered the sleeve, - in a monitoring station, means of identifying

said connection by detecting at least one characteristic parameter

  checking the condition of at least one test lead.

  Advantageously, the monitoring station further comprises means for connecting said means in turn.

  identification of connections to the test cables of the cables of the

monitored bucket, means for identifying a cable when one of its connections is identified and means for emitting

  an alarm signal when said cable is identified.

In accordance with the invention, the humidity detector fitted to each connection is produced in a particularly simple manner by means of at least two sections of insulated conductors respectively connected to the bus wire and to at least one test wire, arranged in contact with 'one of the other and whose insulation is such that its insulation resistance decreases significantly when wet. To give the detector maximum efficiency and minimum bulk, these sections of conductors

  are turns surrounding the wires of the cable.

  According to a first embodiment of the system of the invention, the humidity detector of each connector comprises

from 2 to (n + 1) sections of insulated conductors, one of which is

connected to the omnibus wire and the others of which are connected to as many test wires and in that, in the central station, the connection identification means comprise on the one hand n voltage detectors each of which is connected to a determined test wire of the cable being monitored and delivers a logic signal when the potential of said test wire crosses a predetermined threshold due to the penetration of moisture

  in a fitting, on the other hand an encoder identifying said connection

  cord by combination of said logic signals.

  According to a second embodiment of the system

  of the invention, the humidity detector of

  that connection comprises means (advantageously constituted by a flexible-blade relay relay of the type known as ILS) to cause a short circuit between two wires common to all the sections of the cable and the connection identification means include means measure the loop resistance of these two test leads and identify

said fitting according to the value of said loop resistance.

As for the connector of the invention, it is characterized in that it includes inside the first waterproof and insulating sleeve a second waterproof and insulating sleeve joining it

also the ends of the sheath of the connected cable sections.

  This not only improves the protection of consumers.

  nectors and wires, but it also makes it possible to house the

  humidity sensors between the two sleeves so that

moisture penetration into the first sleeve is detected.

well before the connectors and wires are reached.

  - Other provisions and advantages of the invention!

will appear in the description of exemplary embodiments which

  follows and which refers to the accompanying drawings in which - Figure 1 is a longitudinal section of a connector

  according to the invention and equipped with a humidity detector

  lon the first embodiment defined above; - Figure 2 is a connection diagram of humidity detectors conforming to the detector of Figure 1; - Figure 3 is a diagram in the form of a block diagram of a monitoring station according to the invention; - Figure 4 gives diagrams of some of the organs of the station of Figure 3; 5 - - Figure 5 is a diagram, in the form of a block diagram, of an automatic control which can advantageously equip the station of Figure 3; FIG. 6 is a longitudinal section of a connector fitted with a humidity detector according to the second embodiment defined above;

  - finally Figure 7 is a connection diagram of detector

  humidity meter in accordance with the detector in FIG.

  Consider Figure 1. The fitting 10 which it re-

  present connects two to two, by means of connectors 104, the wires 101 of one section of cable 100 to the wires 103 of another

  section of cable 102. This connection 10 comprises, in the con-

naked, once mounted,

  - a sleeve 11 made of a tight sheath of thermo-polymer

  retractable, covering the ends of the sheath 105 of the section

  section 100 and of the sheath 106 of the section 102; the ends of this sleeve are sealed with layers of bitumen 107, an anti-thermal screen 12 in crepe kraft paper,

  - a covering 13 made of two layers of polychlo- ribbon

vinyl rure.

  According to the invention, the connector 10 comprises a

  additional sealing sleeve 14 surrounding the covering 13.

  This sleeve, in two layers of self-sealing polymer tape,

is applied against cable sheaths 105 and 106 by its ex-

  hoppers which are sealed with layers of bitumen 141.

  According to the invention, a humidity detector is housed inside the anti-thermal screen 12, for example in the annular space existing between this screen and the

  additional sleeve 14. In the embodiment illus-

  tré by Figure 1, this detector 15 has 4 turns 151

  each consisting of an insulated conductor section at the

pier, arranged side by side and in at least partial contact (while Figure 1 shows them separated from each other

to facilitate its examination).

Each turn 151 is connected to a wire 101 or 102 belonging to a reserve pair or quarter (that is to say not used for operation). Each connection is made

  via a wire 161 of a sheet 16 which passes obviously

demment under one end of the sleeve 14 when the coils 151

248 1,462

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  en-ouren4 this one. Connection points scn- Oes -orsades crasées.

  Figure 2 shows examples of connection diagrams.

  connection between the coils 151 and the corresponding wires in different fittings. In the connector marked 10-01, there are only two turns 151, one of which is connected a wire marked 0 and said "common wire" and the other of which is connected 3 a wire called "test" r marked a . The sleeve of fitting 10-06 contains three turns 151, one of which is connected to the comTrrun wire ó em

  two others respectively to sons of tes + and c. The man-

chon of the connection 10-42 contains four turns 151 respectively connected to the wires 0, b, d e-- f. When moisture enters

  in a fitting and decreases the electrical resistance of the

  paper chins of the different turns 151, the fall in resistance

  tance between the common wire $ and the connected test wire (s)

  tees in this connection to the other turns identifies the

says fitting. It suffices to assign a suitable "weight"

tional (for example 1 to wire a, 2 to wire b, .... 32 to wire f) to locate said connection by means of coding of the known type,

  for example an n among m coding or even a binary coding.

  The connection number coding and display unit, located in the monitoring station, is represented by a block

and will be described with reference to FIG. 3.

  If, for example, moisture enters the sleeve of fitting 10-42, the drop in resistance between the wires b, d, f

  on the one hand and the wire 0 on the other hand, corresponds to the number bi-

  naire 101010, whose decimal equivalent 42 is the benchmark of

fitting considered. The six test leads and the common lead

thus put to identify by binary coding 2 exp 7 - 1 = .63

  fittings marked from 1 to 63. In general, the arrangement

  tion of n test wires and an omnibus wire, allowing lo-

ger-in the sleeves of the fittings from 2 to (n + l) coils of

  humidity detection allows monitoring of a number of fittings

equal to (2 exp n-1) of the same cable.

With a connector such as that shown in FIG. 1, the junction of two sections of cable calls, in order, for the following operations: - sliding of the sleeve 11 around one of the sections, - connection of the wires 101 to the wires 103 through connectors 104,

7 - '

- connection by means of brazed twists of the wires 161 of the

  ply 16 to the conductors 101 or 103 belonging to the om wire

nibus and to the test leads, - wrapping by means of the tape 13, - fitting of the sleeve 14 and sealing of its ends

moths, -

  - establishment of i51 turns and connection of these turns to the corresponding wires 161 of the. ply 10 by means of brazed twists, - installation of the thermal barrier 12, - sliding of the sleeve 11 around the splice, heating of this sleeve to obtain its withdrawal, and sealing

of its ends.

  Consider simultaneously Figures 3 and 4 which relate to a monitoring bay arranged for example in a telephone exchange and connected to the bus wires and

  to the test leads of a plurality of cables to be monitored.

This bay allows in particular: - to test each cable in turn by identifying the cable

tested, -

  - trigger an alarm signal when, in a cable - tested, moisture has penetrated into a sleeve,

- Identify said sleeve.

  It therefore gives the indications allowing-

  act quickly to avoid any risk of disruption

  communications as a result of a drop in resistance from iso-

Lately due to humidity.

The monitoring bay includes, for monitoring

launches of N cables marked from 1 to N:

- N selectors 20A, 20B, .... 20N which are in fact ports

  your analog OR. In each, the inputs 202 are connected

  tees to the test wires of the corresponding cable and the input 201 is connected to the bus wire; it was assumed that there are six test leads in each cable; each selector has six outputs 204,

  - a selection command 30 with six outputs 31A, 31B ...

  31N respectively connected to the control inputs of the selectors 20 (FIG. 3 showing only three selectors also only shows three outputs 31A, 31BE and 31N); - N detectors 40A, 4DB, .... 40N; the input of each is connected to an output 205 of the corresponding selector; - an audible alarm device 50, - finally, a connection number display device 60 with six inputs 611 (only three are shown in fig. 3); each input is connected in parallel to the N outputs 204

of the same rank of the selectors 20.

  The selection command 30 comprises N relays of which

The input contacts are all connected to a voltage source.

  continuous voltage of -30 volts and -of which the outputs of the contacts

constitute the control outputs 31A, 31B .... 31N.

We consider more particularly the diagram of one

  selectors 20 given in FIG. 4.

  The omnibus wire J is to the ground of the rack. Each weight test wire a, b ..... f is connected on the one hand to

the anode of a diode 21, the cathode of which is connected to the output

  tie 205, on the other hand to a DC voltage source of -30 volts. Figure 4 further shows, for each wire of

  test, a filtering and over-protection circuit

tensions which includes:

a resistor 22 connected between the test wire and the a-

  node of diode 21, - a capacitor 23 and a diode 24 connected in parallel between the anode of diode 21 and the voltage source of -30 V; diode 24 is obviously connected by its anode to said

source of tension.

  Returning to Figure 3 we see that each detection

  tor 40 comprises a voltage comparator 41 whose input is connected to the output 205 of the corresponding selector 20, a photocoupler 42 whose input is connected to the output of comparator 41 and an indicator light 43 controlled by the output

of the photocoupler 42.

  We now consider, in Figure 4, the partial diagram of that of these detectors 40 which is connected to the output 205 of the door already described. The essential component of this detector is an operational amplifier 411 whose input (+) is connected to output 205 by a resistor 412, whose input (-) is connected via a resistor -9- 413 has an adjustable reference voltage source V1 and of which

  the output controls the light-emitting diode 421 of the photo-

  coupler 42 via a resistor 414. The input (+) of the operational amplifier 411 is also: - connected to the output of this -amplifier by a loop resistor 415,

- connected to the voltage source of -30 V by a circuit

taking, in parallel, a ZENER 416 diode, a capacitor

417 and a resistor 418.

  The roles of these different components (protection,

  hysteresis) are known and there is no need to detail them here.

  We now consider, in Figure 3, the availability

sound alarm signal 50. It comprises: a plurality of monostables 51 each of which has its input connected to the output of one of the photocouplers 42,

- an OR 54 logic gate whose inputs-s are respective-

connected to the outputs of the monostables 51,

  an oscillator 52 generating an infra-acoustic frequency

qw e, - an oscillator 53 generating an acoustic frequency, - a NAND gate 55 whose inputs are respectively connected to the outputs of the OR gate 54, of the oscillator 52 and of the oscillator 53,

  - a power amplifier 56 whose input is connected

tee at the exit of NAND gate 55,

- finally, a speaker 57 connected to the output of the amplifier

ficitor 55.

  We see that the appearance of a logic signal at the

output from any of the photocouplers 42 causes the

  mission by the speaker 57 of a modulated acoustic signal.

We can now briefly describe how

  operate the analog doors 20, the detectors 40 and the

alarm circuit 50.

  When a connection is "dry", that is to say when the humidity has not penetrated into its sleeve, the contact resistance of the detection turns is very high, of the order of several megohms . If all the connections of a cable are "dry", the test leads are therefore brought to the 30 V potential of the- 2481462 -10-

via the diodes 24 and the scrtie 205 is also

  at potential -30 V. When the detection coils 151 (Figures 1 and 2) of a fitting are wet, the insulation resistance between the corresponding test leads and the bus wire drops to a few kilohms o 'a drop in the absolute value of the voltage at output 205. The voltage

  Vi at input (-) of the operational amplifier 411 is re-

glée pou.r that this amplifier then delivers a voltage po-

  sitive to the diode 421 of the photocoupler 42. The latter, whose output transistor is supplied at +5 V delivers a signal at the logic level to the corresponding indicator 43 which lights up

  at the same time as the device 50 emits an alarm signal.

  We now examine, with reference to FIGS. 3 and

  4, the constitution and operation of the advertising system

chage of connection numbers 60. This comprises: - a plurality of detectors 61 whose constitution is similar to that of detectors 41, - a plurality of photocouplers 62 whose inputs are respectively connected to the outputs of detectors 61, -20 - a digital-digital transcoder 63 whose inputs are respectively connected to the outputs of the photocouplers 62,

- finally digital decimal displays 64 in sufficient number-

fisant to be able to display the number of any fitting

  (for 63 connections, obviously 2 displays are enough).

  The input (+) of an operational amplifier 61 de-

finished (for example the amplifier 61a), is connected to all the test wires of the same weight (for example the wires a) of the different cables to be monitored. Connections are made

for each wire (for example wire a) and for each amplifier

  cator by resistor 22, already seen, by resistor 601,

by a diode 603 and by a wire 604a common to all the outputs

  diodes 603 connected to all test leads a. The en

input (-) of each amplifier 61 is connected to a source

delivering an adjustable reference voltage V2.

  In the rest position, the contactors of the relays 31

  of the control 30 are open. When the alarm sounds, the o

  supervisor in charge look at which one

- - 11 -

  LEDs 43 which light up and activate the corresponding relay 31

dant. It thus puts the cathodes of the diodes 602 of the circuit 20 corresponding to the potential -30 volts. Generally speaking,

the outputs of diodes 603 connected to the test wires which -

  remain isolated from the omnibus wire are also at potential -30 volts and the outputs of the corresponding amplifiers 61

  do not deliver a signal since their input (+) is hega-

  tive with respect to their entry (-). On the other hand, in the rac-

  "wet" cord, humidity sensors cause a fall

  the insulation resistance of the test leads therein

  connected, the absolute value of the cathode potential of the di

of the corresponding 603 decreases substantially, the potential of the input (+) of the corresponding amplifiers 61 becomes positive with respect to the potential of the input (-) and each of these amplifiers delivers a signal to the photocoupler 62 which is associated with it. This photocoupler delivers a logic signal to the transcoder 63 and the displays 64 display the number of the

"wet" fitting.

  The device according to the invention which we have just

  to describe with reference to FIGS. 1 to 4, present, with respect to

* port to known devices which use -a simple measurement of the insulation resistance of the test leads, the following advantages it is equally suitable for monitoring cables under

  plastic sheath with plastic insulated wires only for monitoring

launches cables under lead sheath with paper insulator,

- it makes it possible to detect instantly (by the acoustic alarm-

  than 50 and through the LEDs 43) any cable in which a fitting

becomes wet and (by means of the display member 60)

  immediately find the number of this fitting. -

  On the other hand, it requires special care in the connection of the humidity detection turns of the fittings. A mistake. connection causes a connection identification error. In addition, the higher the number of test leads in the same cable, the higher the number of test leads. Said device also has a disadvantage in principle. If two connections of the same cable are simultaneously

1 22481462

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  wet when the gear number is displayed

  cord, a logical summation of the bits of the test leads affected by the fault occurs and the display does not correspond to either of the faulty connections. This drawback is more theoretical than practical because it is extremely rare

  that two fittings of the same cable get wet at the same ins-

  so much, even in the event of complete immersion of a great length

of cable.

The invention does, however, provide a means of avoiding any risk of reciprocal "masking" of two wet fittings by allowing systematic and rapid exploration

  all cables attached to the rack. This means consists of

  sequentially order the openings of the analog doors 40. FIG. 5 shows an example of embodiment of such a sequential control allowing the systematic probing of a

large number of cables.

  We consider figure 5. We recognize the selections

  teurs (doors OR analog) 20 of Figure 3, the inputs -

of test wires 202 of these doors (one door per cable monitors

  lé) and the outputs of said doors connected to the inputs of the

connection number display device 60.

  The doors 20-are opened sequentially-

ment by means of binary counters and demultiplexers. The numerical values below are given by way of example. The

  4-bit counter 320, called primary counter, command 1st de-

  multiplexer 325 with 10 outputs called primary demultiplexer.

  Each output of the demultiplexer 325 is connected to the signal input of a demultiplexer 335 called secondary demultiplexer, also with 16 outputs. -The successive validation of the 16 outputs of each secondary demultiplexer 335 is obtained by means of a binary counter 330 at 4 bits. Each exit from each

  - secondary demultiplexer 335 is connected to the input of

  command from one of the analog OR gates 20.

  The secondary counters 330 are synchronized with the

through a 340-time base through their

  very S. The input S of the secondary counter 320 receives its synchronization signal from the time base 340

  via a divider by 16 marked 345. -

- 13 -

  We see that the sequential control that we have just described allows the sequential opening of 256 doors 20 and consequently the sequential connection of the test wires of 256 cables to the display device 60. It will be recalled that this n '' displays a fitting number (from 1 to 63) only if

  this fitting is "wet". Because the number of cables is

fectively monitored may be less than 256, it is born

  stop providing a reset circuit 350. This one

  * keeps in memory the number of cables monitored

  produced for example by means of coding wheels. Each time the number of pulses delivered by the time base 340 becomes equal. at this number of cables, the circuit 350 delivers a reset signal to the reset inputs of the counter 320 and of the

330 meters.

  The synchronization signal of the time base 340 is also supplied to the synchronization inputs S of a

battery of three 360 decade counters whose outputs include

on the one hand, a cable number display 370 and other

  be part of an organ 375 which can be a mass memory or a printer. The commissioning of this organ is ordered

via an OR 380 logic gate, the

  trées are respectively connected to the output wires 206 common to the analog doors 20, so that said member 375 does not display or record a cable number that

  when the device 60 displays a connection number. The en

control port of an acoustic alarm device 50 (see figure 3) is also connected to the door output

OR 360.

  We mentioned at the beginning of this description

  the major drawbacks of the process of identifying a rac-

  defective cord by means of the measurement of the ohmic insulation resistance of wires chosen as test wires, namely: - that this process cannot be applied to cables with plastic insulation, - that even with cables in lead sheath with insulation

paper, identification is hardly possible.

  The installation in the sleeves of the humidity detector fittings such as the coils 151 (see fig. 1 and 2) r

- 14 -

  avoids the second disadvantage but not the first.

  The invention allows, in a second embodiment,

  to also avoid this first drawback and consequently to

  dentify a wet fitting by measuring the loop resistance between only two test wires. It implements

for this purpose in each connection a humidity detector pro-

  voicing a clear short circuit between these two test leads

  in said fitting when moisture has entered it.

  For this purpose, we consider Figures 5 and 6. The figure

gure 5 is voluntarily incomplete to facilitate its examination.

  These two figures recognize: - the ends of sheaths 105 and 106 of the cable sections 101 and 102, - the conductors 101 and 103 and the connectors 104, - the outer sleeve 11, - two turns 151;

  finally, the ply 16 of the connection wires 161.

  Inside each coupling sleeve 11, there is also a sealed micro-relay 17 of the type known in English as "REED" and in French "ILS" (with switch with flexible blades). Because each connection is identified by measuring the loop resistance and no longer by coding, there is no longer in each connection that two detection turns 151, two test wires a and b common to all the connections and the wire 0. One of the coils 151 is connected to wire 0. The other

  coil 151 is connected to one end of the winding

command 171 of relay ILS 17. The other end of this coil

swim is connected to the test lead a. As for the two blades 172 of the relay 17, they are respectively connected to the test wires a and b. Relay 17 is of the open contact type at rest. It therefore remains open as long as the contact resistance of the turns 151 remains high. When these turns

  are wet, the fall in their contact resistance provo-

that the passage of a current through the winding 171 and the

  + ure of the relay. The wires a and b are therefore short-circuited in the offending connector. This is easily identifiable by the loop resistance measured by means of an ohmeter 70

  housed centrally. It is easy, by means of analog circuits

  ques and numerical BO to directly convert this resistance -:

- 15 -

  loop in connection identification number. This system has, compared to the first system-described with reference to Figures 1 to 5, the advantage of requiring only three wires

  common to all fittings and only two spi-

detection res connected identically in all fittings. The disadvantage is that it can only detect one faulty connection in a cable at a time, ie the one closest to the monitoring bay. But

this drawback is easily avoided by carrying out an ex-

sequential ploration by means of a control device

  similar to that already described with reference to FIG. 5.

  The use of an ILS relay is not primarily

  cipe, the only way to get a short circuit in a rac-

"wet" cord. We could for example substitute a

  semiconductor lead such as a simple connected transistor

so that it is released by the drop in resistance

  tance of contact between the two detection turns 151.

However, the ILS relay has the following advantages over a semiconductor relay: - its contact resistance on closing is zero,

  - it consumes no current at rest.

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Claims (11)

CLAIMS.   1.- Monitoring system for a network of cables   sheathed multi-wire telephones, each cable being made up   killed by a succession of sections of multi-wire cable joined together by fittings, each of which comprises, in a watertight sleeve che joining the ends of the sheath of two sections of cable, a plurality of connectors connecting two by two the wires of these two sections of cable, characterized in that it comprises: - inside the sleeve (11) of each connection (10) a humidity detector (15) connected between on the one hand a determined reserve wire (that is to say a determined-unaffected wire   during operation) of the cable, this wire (0) being chosen as   potential reference and being said "omnibus wire" and other part I to n reserve wires known as "test wires", said detector   tor causing a drop in contact resistance between - the omnibus wire and the test wire or wires when moisture has penetrated inside the sleeve, "- in a monitoring station, means (60) to (70)   identify said fitting by detecting at least one pa-- rameter characterizing the electrical state of at least one test wire. 2. Monitoring system according to claim 1, characterized in that the monitoring station further comprises means (20) for connecting in turn said connection identification means to the test leads of each of the network cables monitored.   3.- surveillance system according to claim 2, characterized in that said connection means are automatic means. 4. A monitoring system according to claim 1 or claim 2, characterized in that the monitoring station further comprises means (43) or (360,370) for identifying a cable when one of its connections is identified. 5. Monitoring system according to claim 2, 3 or 4, characterized in that 'the monitoring station comprises   further carries means (50} for issuing an alarm signal   when said cable is identified. - 17 -   6.- Monitoring system according to any one of   claims 1 to 5, characterized in that the humidity sensor   midity (15) of each connector comprises at least two sections of insulated conductors (151) respectively connected to the bus wire and to a test wire, these two sections of conductors being in contact with each other and their insulator being such that its insulation resistance decreases appreciably when is wet.   7. A monitoring system according to claim 6, characterized in that said sections of conductors are turns surrounding the cable wires. B.- Monitoring system according to claim 6 or claim 7, characterized in that the humidity detector of each connection comprises from 2 to (n + l) sections of   insulated conductors (151), one of which is connected to the omni- buses and the others of which are connected to as many test wires and in that, in the monitoring station, the means connection identification comprises on the one hand n detected voltage testers (61) each of which is connected to a determined test wire of the cable being monitored and delivers a logic signal when the potential of said test wire crosses chit a predetermined threshold as a result of the penetration of humi-   dity in a fitting, on the other hand an encoder (63) -identifier   said connection by combination of said logic signals. 9. A monitoring system according to claim 2 and according to claim 8, characterized in that the means (20) for connecting in turn the identification means for connection to the cables of the monitored network are analog OR gates each of which its inputs connected directly   to the test leads of one of the cables.   10.- Monitoring system according to any one of   claims 1 to 5, characterized in that the humidity sensor   midity of each connection comprises means (17,15.1) of pro-   evoke a short circuit between two test wires common to all sections of cable and in that said means   connection characterization comprise means (70) for measuring   check the loop resistance of these two test leads. - - 1 8 -   11.- surveillance system according to claim 10   on the one hand and claims 6 or 7 on the other hand character-   rized in that said means comprise a relay (17) whose control terminals are respectively connected to the bus wire and to one of the test wires and whose contact terminals are respectively connected to said test wire and to the other test lead. 12.- monitoring system according to claim 10, characterized in that the relay (17) is a relay of the kind THEY. 13.- Monitoring system according to any one of   Claims 1 to 12, characterized in that each connection   (10) comprises, in addition to the waterproof insulating sleeve (11), a man- additional waterproof insulating cap (16) housed inside said sleeve (11) and also joining the ends of the cable section sheaths.   14.- Monitoring system according to claim 13, characterized in that the humidity detector (15) is housed between the two sleeves (11) and (16).