CA1136303A - Switching matrix employing magnetic latching reed switches with double path capability - Google Patents

Abstract

SWITCHING MATRIX EMPLOYING MAGNETIC LATCHING
REED SWITCHES WITH DOUBLE PATH CAPABILITY
ABSTRACT
A switching matrix including a plurality of magnetic latching switching devices selectable over horizontal and vertical conductors. Regulators are provided to limit the current of pulses employed for device selections and an additional regulator shunts a portion of the current during selection of two de-vices to establish multiple paths through the matrix.

Description

3~;~(13 SWITCHING MATRIX EMPLOYING MAGNETIC LATCH:[NG
REED SWITCEIES WITH DOUBLE PATH CAPABILITY
EC HN I CAL F I ELD
The present invention relates to a switching matrix employing electro-magnetic switching device~
and more particularly to a switching matrix employing magnetic latching reed devices with capability for establishing double path connections through the switching matrix.
Generally in known switching matrices em-ploying electro-magnetic switching devices the devices are arranged in a coordinate array at the intersections or cross-points of a number of control conductors extending along the coordinates. Such conductors are usually described as horizontal conductors and vertical conductors or rows and columns respectively.
In most arrangements a number of switching devices are arrayed on a plurality of horizontal conductors and intersected by a number of vertical conductors.
For the purposes of excitation o~ the individual switching devices where the horizontal conductor and vertical co~ductor intersect the windings of the associated switching device are included in both the horizontal and vertical conductor. In order to select a particular switching device a current pulse is applied to the corresponding horizontal ~nd corresponding vertical conductor to energize the excitation windings and thereby operate the selected switching device.
By use of a particular form of electro-magne~ic switching device referred to as a magnetic I ~ . . . -. . .
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~3fi3~3 latching reed switch, once the pulse has been applied the magnetic characterlstics (which will be described further below) will retain the switching device in the operated mode.
Such switching devices are adapted to be released if the excitation winding or windings belong-ing to only the associated horizontal or the associated vertical conductors are energiæed. Thus from the above, when a switching device from a particular cross-point is actuated to close its contact points all oE the switching devices located at other cross-points in the same horizontal and in the same vertical are auto-matically released, since they lack the coincidence of selection of both horizontal and vertical conductor.
Thus it is extremely difficult to establish multiple connections with the switching devices located on the same horiæontal or on the same vertical conductor.
In existing telecommunication systems which employ the magnetic latching reed device as a network element it is Erequently desirable to establish parallel connections for test and monitoring purposes. In systems such as the No. 2 EAX System manufactured by GTE Automatic Electric and in the No. 2 ESS System manufactured by Western Electric such test and monitoring connections are made via a dedicated matrix called a "Test Vertical~' access. A description of this type of dedicated matrix is found in the Bell System Technical Journal, Volume 48, No. 8, pages 2677-2678.
In other magnetic non-latching~ cross-point or cross-bar devices such as reed relays, relay cross-point switches or cross-bar switches, the cross-points are electrically latched and thus two cross-points in either of the same horiæontal ox the same vertical can be operated and both electrically latched up.
In such an arrangement where each reed type switching device is bridged across the intersection of the horizon-tal and vertical conductors, for a single connection a positive potential is applied to one of the horizontal conductors and a negative potential to one of the vertical , .
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conductors thus allowing a single cross-point to operate.
When a double connection is required, a positive potential is applied to two horizontal conductors and to one vertical conductor. This can be done simultaneously or successively and thus two cross-points on the same vertical are operated, establishing the desired double connection. Similar techniques are employed with relay cross-bars or cross point switches.
Many contemporary switching matrices have employed the use of magnetic latching reed devices because of their desirable quality of eliminating the necessity for holding currents. These devices typically consist of one or more sealed reeds whose blades are made of a hysteresis type magnetic material which may be magnetized in either direction and retain that state, without external energy sources. The excitation portion typically consists of a four winding coil with two primary and two secondary windings. Each primary winding has twice the number of turns and is in opposition to its associated secondary winding. The primary and secondary windings are usually connected in series.
The device also includes a shunt plate to divide it into two separate magnetic fields. The windings are further arranged so that one primary winding is on one side of the shunt plate and its associated series connected oppositely wound secondary winding with half the number of turns as located on the other side.
The remaining primary and secondary windings are arranged so as to compliment the first two windings. That is to say that the primary winding is on the opposite side and on the same side of the shunt plate as the secondary winding previously referred to with the second series wound secondary on the opposite side of the shunt plate from its own primary and opposite to and on the same side of the shunt plate as the previously mentioned primary winding.
When a current pulse is passed through all four windings the currents generated on both sides .:
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, ~3~ 3 of the shunt plate are in the same direction causing the upper and lower reed blades to be properly mag-netized and thus latched. However when a current pulse is passed through only one set of windings either the upper or lower set of reed blades are magnetized in the opposite direction to their previous state and the reed blades open.
Because of the four winding design of the magnetic latching reed, the most suitable technique for operating an individual device is in a matrix ar-rangement; that is to connect all devices in series on the horizontal and vertical conductors. In this manner when a current pulse is applied to one horizontal conductor and returned to one vertical conductor, only the magnetic latching reed device at the intersection of the horizontal and vertical conductors has both its windings pulsed and operated. All other magnetic latching reed devices along the horizontal and vertical conductors have only one set of primary and secondary windings pulsed and would therefore release i~ they were operated or would remain released. This type of marking is referred to as destructive marking wherein all non-selective cross-points release if not operated.
The establishment of double path connections through a switching matrix employing magnetic latching switching devices is disclosed in U.S. Patent 3,953,813 to N. Yano et al. To accomplish this end result the Yano patent teaches the use of magnetic latching switching devices of a non-standard construction with four windings all of equal size. The selection arrangement is also different using double horizontal and vertical paths through the matrix with all primary windings connected in series first and then returned through all secondary windings. Other specific requirements not found in conventional switching matrices include provision of a special short circuiting switch employed during double path selection. This arrangement also requires the application of consecutive pulses to establish a double path connection.

-~ 1~3~ 3 .~ ~ 5 The conventional operation outlined abovemakes it difficult where desired to establish multiple connections of any switching devices located on the - same horizontal or on the same vertical. If for example one attempted to apply a pulse to two horizontal conductors simultaneously, and return the pulses to one vertical conductor the vertical would carry twice the horizontal currents. This would then cause lO0~ imbalance between the vertical and horizontal windings of the selected devices and no reeds would operate. To operate a single switching device after selection, by application of a current pulse to one horizontal and one vertical conductor, twice the current flows in both primary windings as appears in the oppositely wound second-aries. The net result is equal current flows on both sides of the shunt plate (upper and lower half) creating a balanced condition. The switching device operates because both upper and lower half, have positive ampere-turn fields in the same direction.
In an attempt to operate two switching devices, twice the current flowed in one direction of the upper half as that flowing in an opposite direction in the lower half of the switching device on one of the se-lected horizontal conductors. Similarly twice the current flows in one direction to that flowing in the opposite direction of the switching device on a second selected horizontal conductor. While in the vertical conductor because the windings of two switching devices are included in series; the net result is to have zero ~ 30 current flowing in the upper windings of each cross-; point and three times the current flowing in the lower half so that a current imbalance exists, resulting in neither cross-point operating due to lack of mag-~ netic fields being generated in the upper half of each - 35 of the selected cross-point devices. Accordingly, it is the object of the present invention to cancel ~ the destructive marking phenomenon by overcoming the ; problem of current imbalance between horizontal and ~' ."
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~L~3~ 3 vertical conductors when two horizontals and one ver-tical are pulsed to establish a dual path through a switching matrix employing magnetic latching switching devices of conventional construction.
DISCLOSURE OF THE INV~NTION
The present invention consists of a switching matrix comprising a plurality of magnetic latching switching devices each haviny four windings with two windings being included in the horizontal conductors of the switching matrix and two windings included in the vertical conductors. In addition all horizontal conductors and all vertical conductors (and thus the windings of all switching devices) are connected to a separate conductor, all horizontal conductors are connected to a dual current regulator, all vertical conductors are connected to a second current regulator and the separate conductor is connected to a third current regulator. A current balancer circuit also exists between the regulators connected to the vertical conductors and to the separate conductor. The current regulator connected to the horizontal conductors operates to regulate the horizontal current at either a first chosen level or a second level (twice that of the first) depending on whether a single or double cross-point operation is required. The regulator connectedto the vertical conductors regulates the current to the same first predetermined level when returned from the vertical conductors. When a double connection is desired by selection of two cross-points the third regulator connected to the separate conductor is acti-vated to regulate the shun-t current to the same value as the preselected value occurring on the vertical conductor s .
By providing accurate current regulators to control the selection pulses for the present matrix, the current is sufficiently balanced to obtain reliable two device operation and thus provide multiple con-nections through the matrix. In telephone systems .~:
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. -a single control lead only is required in each matrix stage in addition to the required accurate current sources provided on a common basis.
With the outlined arrangement the current flowing through the windings of the selected devices on the horizontal conductors is similar to that out-lined above in the prior art, that is to say that twice the amount of current flows in the upper half of each device and in a direction opposite to that flowing in the lower half, with half the value flowing in each of the devices on the windings of those devices on the vertical conductor totaling an amount equal to the current flowing in each horizontal conductor.
The other half of the current that would normally flow through the vertical conductor being shunted over the separate shunt path described above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of the control portion of a switching matrix employing magnetic latching switching devices in accordance with the present inventlon .
FIG. 2 is a combined cross section view and schematic diagram of a ma~netic latching switching device typical of those employed as switching devices in the switching matrix of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to FIG. 1 a switching matrix in accordance with the present invention is shown.
The matrix consists of a number of magnetic latching devices 100, 101, etc. disposed at the intersections - of a number of horizontal conductors X0, Xl and X9 and a number of vertical conductors Y0, Yl and Y9.
As shown in FIG. 1 additional switching devices could be provided and located along the same conductors as well as along additional hori~ontal and vertical con-ductors wh:Lch have not been shown. The minimum size for such a switching matrix obviously would be four switchins devices with no theoretical maximum limitation ~ , :, ~

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:. . :, 3~3 on the number of devices employed~ It should be fur-ther noted that the number of horizontal and vertical cGnductors do not necessarily have to be equal.
Each of the horizontal conductors X0, Xl and X9 are connected through an associated diode 120, 121 and 129 respectively, which insure the proper direc-tion of current flow over the hori~ontal conductors, to dual regulator 150. Each vertical conductor Y0, Yl and Y9 are connected through an associated diode 130, 131 and 139 respectively to a second regulator 160. ~ach of the horizontal conductors X0, Xl and X9 and each of the vertical conductors Y0, Yl and Y9 are also connected at its end opposite to the end con-nected to the associated regulators 150 and 160, to a common conductor 5H which through an associated diode 140 is connected to a third regulator 170.
Each of the switching devices 100, 101, etc.
are connected to the horizontal and vertical conductors by means of a series connection through the included windings. By reference to switching device 100 it may be seen that the horizontal conductor X0 is con-nected through a primary winding lOOA in series with a secondary winding lOOB to switching device 101, etcO
Primary winding lOOA has twice the number of windings as secondary winding lOOB and is wound in the opposite direction. Similarly the vertical conductor ~0 is connected in series through other devices and in series through the secondary winding lOOC in series with the primary winding lOOD. Again primary winding 100D has twice the turns of secondary winding lOOC which are wound in opposite directions to each other. Similar connections are employed for all of the switching devices in the matrix of the present invention. The switching contacts of each of the switching de~ices 100, 101, etc. have not been shown in Figure 1, since the present invention is concerned primarily with the control of the switching devices whereby selected paths therethrough may be established.
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The regulators 150, 160 and 170 are all con-ventional current regulators limiting the flow of current therethrough in any well known manner. Each regulator is connected to a common pulse source (not shown). The details of the pulse source have not been disclosed since they do not form a part of the present invention and the construction o~ same is well known to those skilled in the art.
Pulses for operation oE the switching devices from the pulse source are regulated by the connected regulators 150, 160 and 170 in a manner described below.
The speciEic selection of the desired devices to be operated in the matrix may be made by means of a central processor or similar controller (not shown) connected to each of the regulators. The details of operation of such seleckion and the connections thereto do not form a portion of the present invention but to aid in under-standing switching contacts A0, Al and A9 and B0, Bl and B9 have been shown as means for selecting the horizontal and vertical paths respectively. The only specific requirements of the present invention are that dual regulator 150 which is shown as a positive regulator limit the current on a selective basis to a first value when a single switching device is selected and to twice that same value when two devices are selected, to establish a multiple connection through the matrix. This may be done automatically or under the control of a central processor. In one embodiment of the present invention these limits were established as 5.8 amperes for a single selection or 11.6 amperes for dual device operation. The negative regulators 160 and 170 in the same embodiment provide regulation to limit the currents flowing therethrough to 5.8 amperes.
Since regulator 170 is operated only when it is desired to establish a dual path through the switching matrix a separate lead "shunt-on' connected to the afore-mentioned central processor or controller is provided to activate regulator 170.

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L3~3V3 Regulators 160 and 170 are connected via a balance circuit which insures that both regulators when oeprated simultaneously regulate to the same current limit. The techniques of balance to maintain such e~ual regulation may be any of several well known in the art and do not form a portion of the pr~sent invention.
A more thorough understanding of the switching devices included in the switching matrix of the present invention may be had by reference to FIG. 2. The magnetic latching reed devices as utilized in one embodiment of the present invention each include two sealed reed units 205 and 206 which provide means for completing circuit connections across two signal lead such as employed for the talking path in a con-ventional telephone system. The details of the signal path arrangement of the present matrix have not been shown P~
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::-~3~ 3 since the present invention is directed to control of the switching matrix, rather than to its application in any specific environment.
The blades or switching contacts of each of these reeds are made of a hysteresis type magnetic material which can be magnetized in either direction, retaining that magnetic state without external energy sources. Included is a four winding coil with a primary winding 201 connected in series with a secondary winding 202 and a primary winding 204 connected in series with a secondary winding 203. Primary windings 201 and 204 each have twice the number of turns as the secondary windings and are wound in the same direction as each other and opposite to the direction of the windings of each of the secondary windings 202 and 203 respectively.
Also included is a shunt plate 207 which provides separation between the magnetic fields generated on either side. The direction of current flow in each of the windings is as shown in FIG. 2.
~rom the above it can be seen that when a current pulse is passed through all four windings 201 through 204 the amount of current generated on both sides of the shunt plate is in the same direction with the amount of current in each primary being twice that in each secondary causing magnetization of the upper and lower reed blades in the appropria~e direction to cause them to be operated and thus latched. However if current is passed only through one set of windings from either the hori~ontal or the vertical conductors either the upper or lower set of reed blades will be magnetized in the opposite direction of their previous state and the reed blades will open.
Referring again to FIG. 1 operation of a single cross-point will be described. If it is desired for example to operate switching device 100 the associated c~ntral processor or controller (not shown) would by selectively controlling the outputs of regulators 150 and 160 cause a pulse to be applied over conductors X0 (by operating switching contacts A0 and B0 or any other similar well known switching means~ and Y0. The hori~ontal conductor -. : .. . :

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X0 being connected to primary winding 100A and secondary winding 100B and the primary winding 100D and 100C being connected in series to the vertical conductor Y0. Since the current flow in the upper and lower half of the switch-ing device as referred to above are both in the samedirection the device will ope:rate. This can be demon-strated by the following:
UPPER HALF LOWER ElALF
I ~OR. +2AT ~AT
I VER. -AT ~2AT

+AT = +AT
IE it is desirable to operate two switching devices such as 100 and 110 operation will be as follows:
Again the associated central processor or controller will operate to control the output of regulator 150 via switching contacts A0 and Al and cause a current flow over horizontal conductors X0 and Xl to the included primary and secondary windings of switching devices 100 and 110. The output of regulator 160 will be applied at switching contact B0 and current will flow over conductor Y0 through the included primary and secondary windings of switching devices 100 and 110. At this time over the "shunt-on" lead a signal will also be transmitted from the controller or central processor to regulator 170 which will operate to provide a shunt path SN for current attempting to flow over vertical conductor Y0. Because the current limiting characteristics or regulators 160 and 170 are similar and because of the inclusion of the balance circuit, half of that current will be shunted over conductor SH to regulator 170, thus the total current flowing over the primary and secondary windings of switching devices 100 and 110 will not be doubled as in the prior art, with the flow of current over horizontal conductors X0 and Xl, but will rather be ; equal in each device to the current flow in the hori-zontal conductors. This balanced current flow will of course cause operation of switching devices 100 .~

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~3 -` ~ 3 and 110 to establish the desired dual paths through the swi-tching matrix. This operation can be expressed as follows:

UPPER LOWER UPPER LOWER
HALF HALF HALF HALF
I HOR (100) +2AT ~AT
I HOR (110) ~2AT -AT
(100 + 110) -2AT ~4AT -2AT +4AT
I VER - 2 ~~~ 2 1 0 . _ ___ +AT = ~AT +AT = +AT
INDUSTRIAL APPLICABILITY
While the switching matrix of the present ; invention has been described in connection with its application to a telephone switching network it would be obvious that the invention can find equal use in a number of other applications including computers, industrial control systems, etc. In short any applica-tion where it is desirable to provide a switching matrix over which to establish dual circuit connections while employing the advantages of magnetic latching switching devices. Accordingly, although but a single version of the present invention has been shown, it will be obvious to those skilled in the art that numerous modifications may be made without departing from the spirit and scope of the invention, which shall be limited only by the claims appended hereto.
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Claims (13)

WHAT IS CLAIMED IS:

1. A switching matrix comprising: a plurality of switching devices, each including a plurality of switch-ing elements and first, second, third and fourth windings for generating magnetic control fields for controlling the operation of said switching elements, a plurality of horizontal conductors each including said first and second windings of at least two of said switching elements, a plurality of vertical conductors each including said third and fourth windings of at least two of said switching elements, the polarity of said first, second, third and fourth windings being such that when a current pulse is passed through said horizontal and vertical conductors said second and third winding generate magnetic fields in a direction opposite to that generated by said first and fourth windings and a pulse source operated to generate pulses to operate a selected one of said switching elements and alternately to operate a selected two of said switch-ing elements, the improvement comprising: current lim-iting means connected to said pulse source and including circuit connections to said horizontal and vertical con-ductors for limiting the current of pulses passed through said conductors.

2. A switching matrix as claimed in claim 1, wherein: said current limiting means comprise a plu-rality of current regulators.

3. A switching matrix as claimed in claim 2, wherein: said plurality of current regulators include first, second and third regulators.

4. A switching matrix as claimed in claim 3, wherein: said first regulator includes a plurality of circuit connections each to a different one of said horizontal conductors; and said first regulator is operated to limit the current of pulses transmitted over selected horizontal conductors.

5. A switching matrix as claimed in claim 3, wherein: said first regulator includes a plurality of circuit connections each to a different one of said horizontal conductors; and said first regulator is operated to limit the current of pulses transmitted over a selected one of said horizontal conductors to a first predetermined limit; and further operated to limit the current of pulses transmitted over a selected two of said horizontal conductors to a second predeter-mined limit.

6. A switching matrix as claimed in claims 4 and 5, wherein: said circuit connections each include unidirectional conducting means.

7. A switching matrix as claimed in claim 3, wherein: said second regulator includes a plurality of circuit connections each to a different one of said vertical conductors; and said second regulator is operated to limit the current of pulses transmitted over a selected one of said vertical conductors.

8. A switching matrix as claimed in claim 7, wherein: said circuit connections each include unidirec-tional conducting means.

9. A switching matrix as claimed in claim 3, wherein: said third regulator includes a circuit connec-tion to each of said horizontal and vertical conducotrs;
and said third regulator is operated to limit the cur-rent of pulses transmitted over a selected one of said vertical conductors.

10. A switching matrix as claimed in claim 7, wherein: said circuit connection includes unidirec-tional conducting means.

11. A switching matrix as claimed in claim 9, wherein: said third regulator further includes a circuit connection to said second regulator; and said third regulator is operated to shunt half the current of pulses transmitted over a selected one of said vertical conductors.

12. A switching matrix as claimed in claim 1, wherein: said switching elements are of magnetic material and said elements are reversible in magne-tization and capable of retaining residual magnetiza-tion.

13. A switching matrix as claimed in claim 12, wherein: said switching elements have a magnetic self-holding function.