US3562602A

US3562602A - Control circuit and method of control for latching relay

Info

Publication number: US3562602A
Application number: US690354A
Authority: US
Inventors: John G Mlacak; Doron Cohen
Original assignee: Northern Electric Co Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1967-12-13
Filing date: 1967-12-13
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09
Also published as: DE1803369B2; DE1803369C3; NL6815981A; SE357096B; NL148180B; JPS5147020B1; BE722927A; DE1803369A1; GB1191082A

Abstract

Circuitry is designed to allow a change in potential level to cause latching or to cause unlatching of an electromechanical relay, with the change in potential level being amplified and supplied to the relay latching and unlatching circuit through a step-up transformer.

Description

United States Patent u|13,562,602

[72] Inventors John G. Mlacak [50] Field ofSear-eh 317/154 Kanata, Ontario; Doron Cohen, Brampton, Ontario, Canada ['56] Cited [21] Appl. No. 690,354 UNITED STATES PATENTS' 1 Filed [kc-13,1967 2,982,887 5/1961 Seeley 317/1s4x [45] Patented Feb. 9,1971 [73] Assignee Northern Electric Company Limited f'm' f' M Mum Quebec Canada Assistant Examiner-William J. SmIth Attorney-Westell & Hanley [54] CONTROL CIRCUIT AND METHOD OF CONTROL FOR LATCIIING RELAY ABSTRACT: Clrcurtry 15 designed to allow a change In poten- Chin" nnwing tial level to cause latching or to cause unlatching of an elec- [52] [1.8. CI. 31 7/154, tromechanical relay, with the change in potential level being 317/ I54 amplified and supplied to the relay latching and unlatching [51 Int. Cl..... lltllh 47/04 circuit through a step-up transformer.

AAA

PATENTEU FEB 9197! INVEN'IUR.

JOHN G MLACAK WOHEN ATTORNEY CONTROL CIRCUIT AND METHODOF CONTROL FOR LATCHING RELAY This invention relates to means and method for controlling the operating and releasing of an electromagnetic latching relay of the type which, when operated is adapted and connected to latch itself on through one of its main circuit connections and one of its own contacts so that it may remain energized, in spite of the termination of the original energizing current. Such relay must be released by interruption of the current flowing through the relay coil of the latching circuit.

In control and switching systems it is quite often desirable that a relay may be actuated by a signal or pulse of limited duration and that it will then remain in the state to which it is actuated after the termination of the signal or pulse and until caused by another controlsignal to release to its'original state.

Thus the relay used must have some sort of memory to memorize the last control instruction or in other words to remain in the state instructed after the cessation of the instruction.

One approach to this has been the use of a magnetic latching relay. The memory effect is achieved through the magnetic properties of a relay core and the spring structure of such relays. The relay is designed so that when pulsed by a predetermined voltage the relay will latch due to remanence magnetism in the core, resulting from the original pulse. For release, a carefully timed pulse of the opposite sense is applied to the relay coil and the core is then demagnetized removing the holding coercive force. Considerable difficulties have been encountered in the operation of such relays due to the necessity of careful timing of the release pulse. lf the release pulse is too short the flux in the core will change with the incidence of the pulse but with the removal of the pulse will return almost to its original state on the hysteresis curve leaving enough force for the relay to stay operated and the relay therefore fails to release. If the release pulse is too long the state of the core will travel to the other side of the hysteresis curve and the relay will release but will subsequently reoperate so that sustained release is not obtained.

Electronic latching has also been considered where an electronic circuit is attached to an electromagnetic relay to give it the latching property but such circuitry in large switching systems has been found to be extremely expensive and to render impractical many switching systems on this basis.

The mode of latching with which this invention is concerned is electrical latching which comprises an electromagnetic relay having one of its contacts connected so that when the relay is operated it is latched on through its own contact. This mode of latching is of course well known and no claim is made herein to the development thereof. However, this invention concerns a circuit and a method of activating such an electrical latching relay to allow for its use with switching systems and with control signals or changes in control signals of limited magnitude and duration. The method for achieving latching or electrical latching of the relay and the means therefor is also available for releasing the relay and means are provided herein for selectively controllable operate and release operations.

The control circuitry and method also permit easier and less complex detection of the state (i.e. operated or released) of the relay.

It is an object of this invention to provide a control circuit adapted to receive a change of amplitude in a control signal indicating an instruction to latch the relay, and to magnify the effect of such change in amplitude to produce a pulse of sufficient duration and magnitude to achieve the latching operatron.

It is an object of this invention to provide similar circuitry to that described in the preceding paragraph for achieving the releasing operation and, in a preferred embodiment to disclose means whereby with both release and operate circuits means may be provided for preselecting one but not both of the release and operate operations whereby said preselection and the incidence of a timing pulse will cause the change of signal amplitude in the circuit designed to achieve the desired change of relay state. Preferably the length of the timing pulse is used to determine the length of the operate or release pulse with the circuitry being designed to produce a pulse of the necessary magnitude and shape to release or open the relay during the controlled pulse duration.

It is an object of this invention to provide means whereby a change in amplitude of a control signal (and by change in amplitude" we include the situation where the change is to or from zero amplitude or to or from zero signal) indicating a desire to operate or to release the relay, is stepped up in a step-up transformer and applied as a pulse to the relay as a potential alternatively:

a. tending to cause flow through the relay in the holding current directionfor the latching operation;

b. tending to decrease flow through the relay in the holding current directionfor the release operation.

it is an object of the invention to provide means whereby the change in the control signal indicating a request to operate or a request to release the relay is caused to change the state I of a transistor whose power circuit thereupon alters the state of current flow through the primary of a step-up transformer and where this change of state is applied as a pulse to the relay in'a sense to (1) cause current flow therethrough in the holding current sense and of sufficient magnitude and duration to operate the relay or (2) reduce current flow therethrough in the holding current sense to a sufficient degree to cause release of the relay.

It is an object of the invention to provide a method of operating or releasing a latching electromagnetic relay comprising providing a change in signal level to indicate the request for operation or release, and causing said change to alter the condition of current flow in the primary of a step-up transformer and applying the pulse thereby produced in the secondary of the step-up transformer to a relay to initiate or decrease the current therethrough in the holding current direction depending on whether the operate or release opera- 1 10. It will be understood that the relay will have other contacts 'not shown which perform the switching functions desired to be controlled by the relay. A line 14 connects the control circuit to be described to the relay latching circuit between relay 10 and resistance 12. The resistance 12 not only limits the holding current, but, connected between line 14 and the latching contact potential prevents control signals appearing along line 14 from being shorted to ground before they affect the relay operation. Four normally closed relay contacts 17 are shown in the line 14. These have no intrinsic bearing on the operation of the invention and should be considered as closed. Their only purpose is to respectively operate at the control of corresponding control relays (not shown) so that the opening of any of contacts 17 will prevent application of a control signal to the latching relay at times when it is desired to inhibit the operation or release of relay 10 for reasons extrinsic to the circuitry shown.

Line 14 is connected to B; which may be the same value as B, through a resistance 18, a condenser 20 and a resistance 22 in series to By which may be the same as B, but may be different in accord with the requirements of specific circuit design. The above components are described out of logical sequence to clarify the fact that the main purpose of the circuitry shown to the left of this line indicated as line A-A is designed to operate the relay and the main purpose of the circuit to the right of line A-A is designed to release the relay.

Considering, first, the circuit to the left side of line A-A a signal input line is connected to 8+ supply line 102 through a diode 104 and resistance 106 in series with the diode poled to conduct when line 102 is higher than the signal input on line 100. The junction between resistance 106 and diode 104 is connected through diode 108 to the base of an NPN transistor 110 and the base is also connected to ground through a resistor 111. The diode 108 is poled to conduct when the potential on the side thereof remote from the base of transistor 110 is higher than at the base of the transistor. The connection between diode 108 and the base of transistor 110 may be optionally connected to signal inputs 112 and 114 through diodes 117 and 118 respectively with each of the diodes being poled to conduct in the direction toward its respective input.

it will be later seen that the operation of the invention will be described ignoring the presence of the inputs 112 and 114, i.e. considering them as unconnected and later their significance in the circuit will be discussed.

The collector of transistor 110 is connected to B+ line 102 through resistor 113. The emitter of transistor 110 is connected to the base of an NPN transistor 116 by a diode 119 with the diode poled to conduct when the potential at the 110 emitter is higher than the 116 base. The 116 base is also connected to ground through a resistor 120. The collector of transistor 116 is connected through resistance 122, zener diode 126 and a diode 128 in series to the base of transistor 110. The zener diode 126 is poled to provide its design voltage drop to potentials higher at the collector of 116 than the base I of 110 and the diode 128 is poled to conduct for potentials higher in the same sense. The collector of transistor 116 is also Ct nnected through the primary of a step-up transformer 130 to the 13+ line 102 and the dots on the transformer windings indicate the-relative polarity of voltage changes between primary and secondary. One end of secondary of transformer 130 is connected to B through resistance 22 and the connection between the secondary and resistance 22 is connected to ground through a condenser 134. The last named condenser acts as a ground to unwanted high frequency noise appearing in the transformer secondary.

Connected in parallel with the secondary of transformer 130 is a series circuit comprising diode 136, resistance 138 and aparallel circuit with the parallel circuit comprising the condenser 140 and the resistance 142 in parallel. The diode 136 is poled to conduct when the potential at its connection to resistance 138 is higher than at its connection to the secondary of transformer 130. The connection between the secondary of transformer 130 and diode 136 (that is the end of the transformer secondary winding electrically remote from B is connected to line 14 (at its junction to line 16) through a resistor 144 and a condenser 146 in parallel; and then in series through a diode 148 with the diode being poled to conduct when the potential at the secondary of transformer 130 is higher than the potential on line 14.

This is the circuit for operating," i.e. latching the relay and there will now be described the counterpart circuit for releasing or unlatching the relay and it will be found that this circuitry is substantially the same as that just described subject to the fact that the diode 248 is oppositely poled (relative to line 14) to its counterpart 148 and that the relative polarities of primary and secondary of transformer 230 is theopposite of such polarities for its counterpart transformer 130 as indicated by the dots adjacent the transformer winding.

Components in the circuit to the right of line A-A which are analogous to components in the circuit to the left thereof, will be given numerical designations one hundred higher than the elements to which they are analogous.

Considering, now, the circuit to the right hand side of line A-A a signal input line 200 is connected to B+ supply line 102, through a diode 204 and resistance 206 in series with the diode poled to conduct when line 102 is higher than the signal input on line 200. The junction between resistance 206 and diode 204 is connected through diode 208 to the base of an NPN transistor 210 and the base is also connected to ground through a resistor 211. The diode 208 is poled to conduct when the potential on the side thereof remote from the base of transistor 210 is higher than at the base of the transistor. The connection between diode 208 and the base of transistor 210 may be optionally connected to signal inputs 212 and 214 through

diodes

217 and 218 respectively with each of the diodes being poled to conduct in the direction toward its respective input.

It will be later seen that the operation of the invention will be described ignoring the presence ofthe inputs 212 and 214. i.e. considering them as unconnected and later their significance in the circuit will be discussed.

The collector of transistor 210 is connected to B+ line 102 through resistor 213. The emitter of transistor 210 is connected to the base of an NPN transistor 216 by a diode 219 with the diode poled to conduct when the potential at the 210 emitter is higher than the 216 base. The 216 base is also connected to ground through a resistor 220. The collector of transistor 216 is connected through resistance 222, and zener diode 226 and a diode 228 in series to the base of transistor 210. The zener diode 226 is poled to provide its design voltage drop to potentials higher at the collector of 216 than the base of 210 and the diode 228 is poled to conduct for potentials higher on the same side. The collector of transistor 216 is also connected through the primary of a step-up transformer 230 to the B+ line 102 and the dots on the transformer indicate the relative polarity of voltage changes between primary and secondary. It will be noted that the polarity is the opposite of that for transistor 130. One (the dotted) end of secondary of transformer 230 is connected to B through resistance 22.

Connected in parallel with the secondary of transformer 230 is a series circuit comprising diode 236, resistance 238 and a parallel circuit with the parallel circuit comprising the condenser 240 and the resistance 242 in parallel. The diode 236 is poled to conduct when the potential at its connection to resistance 238 is lower than at its connection to the secondary of transformer 230. The connection between the secondary of transformer 230 and diode 236 is connected to line 14 (at its junction to line 16) through a resistor 244 and a condenser 246 in parallel and then in series with a diode 248 with the diode being poled to conduct when the potential at the nondotted end of the secondary of transformer 230 is lower than the potential at the junction of lines 14 and 16, this being opposite to the polarity of diode 148 relative to the junction of lines 14 and 16.

Line 16 is connectable to a detector for detecting the state of relay 10 and for reporting to the control circuitry. The detector forms no part of the present invention so is not described here, but may be of any well known type of potential level detector designed to detect the difference of potential on the line 14 between that existing in the conducting and nonconducting states of relay 10. One of the advantages of the use of an electromagnetic latching relay with the control system herein discussed is that the existing state of the relay may be easily detected, at any time. With magnetic latching relays on the other hand it has been found impractical to determine the relay state hence it has been necessary with such relays to detect the transition between one state and the other and this has been a more difficult and expensive propositron.

The operation of the circuitry so far discussed will now be described.

Initially it will be assumed that terminals 112, 114, 212, 214 are open circuited, and that the relay is deenergized. Transistor 110 would be biased into conduction by the potential of its base obtained by the voltage divider formed by resistances 106 and 111 between 8+ and ground, however with the biasing as shown, it is assumed that the quiescent state of the signal on line is sufiiciently less positive than B+ that through the action of diode 104, this potential applied across diode 108 and resistance 111 biases transistor to nonconduction. Similar conditions apply on the release side of the circuitry. The bias which would be applied by the conduction from B+ through

resistances

206 and 211 to ground is not applied due to the design arrangement that the control signal on line 200 shall be sufficiently less positive than B+ that through the action of diode 204 transistor 210 is biased off.

It will be seen that when transistor 110 is nonconducting the base of transistor 116 will have the same potential as the emitter and that the transistor will be nonconducting, similarly when transistor 210 is nonconducting, there is no base-emitter potential on transistor 216 and the latter is biased off.

The incidence of a positive signal on line 100 sufficiently positive to cause conduction in transistor 110 due to the greater potential acting across diode 108 and resistor 111, acts as a command for the relay to close. When such signal is received, conduction in transistor 110 biases the base of transistor 116 causing the latter transistor to conduct. Transistor 116 is preferably a transistor switch and the change to the conduction state is rapid. Conduction creates a surge of current through the primary of transformer 130 and drives the potential of the primary remote from line 102 (the nondotted end) negative. The potential drop across the primary is stepped up by the turns ratio to and in the relative polarity indicated by the dots. Since the nondotted end of the secondary is tied to B the potential of the dotted end of the secondary is driven positive by an amount determined by the magnitude of the input surge and the turns ratio. The turns ratio will therefore be calculated to achieve the magnitude required for the operate pulse. The pulse is shaped during its passage through condenser 146. and resistance 144 which may be of selected values to provide the desired shaping for the pulse. Preferably both C and R will be relatively large so that the initial surge of the pulse is substantially all through the condenser and the shape of the pulse tends to be sharpened. The positive pulse passes through diode 148 and the circuitry is designed so that the pulse shall be sufficiently positive relative to B,- to achieve energization of the relay during the duration of the pulse passing through diode 148. 1

The main problem of energizing relay is overcoming the inductance of its coil and the pulse is therefore (in accord with design and its mode of formation) designed to have a large amplitude in its initial period and decreasing amplitude.

thereafter. As a result of the application of the pulse, relay 10 is energized (and it will be noted that the pulse causing such energization causes current flow through the relay in the same direction as the alternate holding current will be) closing its latching contact 10-1. When the pulse terminates therefore the relay will be held in operative position by the holding current from ground through closed contacts 101, resistance 12 with relay 10 to B,.

In relation to the magnitude of the actuating pulse, it will be noted that some of this is dissipated through diode 248, resistance 244 and condenser 246, in parallel, diode 236 resistance 238, condenser 240, resistance 242 (and to someextent through the secondary of transformer 230) and then through resistance 22 to B The impedance of this last defined route is of course designed so that such dissipation will be minimal, having regard to the other necessary functions of the components. However the pulse magnitude must be designed with such dissipation inmind.

It is desirable that the pulse, which achieves the operation of relay 10 shall terminate at the time the flow of holding current commences and further that the current created by the pulse at this time shall be as near as possible to the holding current, so that there shall be as few spikes as possible in the relay current during the transition. The current magnitude at termination is achieved by pulse shaping and the length of the pulse is determined by termination of the command pulse on line 100. It will be noted that while it might be thought that the pulse would be terminated by the natural reverse swing in the transformer, it has been found preferable to provide pulses of such duration that the relay would operate before the natural transformer reverse swing would commence. lt has also been found preferable to dampen the transformer so that there is in fact no material natural reverse swing of the transformer. Hence the pulse is terminated by reverse swing caused by termination of the command signal on line 100 rather than by the natural return swing of the transformer. On termination of the command signal the signal on line 100 goes negative stopping conduction in transistor which inturn cuts off conduction in transistor 116. This transition takes place somewhat more slowly than described since the resultant positive swing of the nondotted end of the primary, causes a surge through the zener diode 126, maintaining transistor 110 and hence transistor 116 conducting for a somewhat longer period than would otherwise be the case and. in effect making more gradual, the reverse voltage swing.

The reverse voltage swing in the primary of transformer creates a similar swing in the secondary which causes the pulse applied across the diode 148 to'end when the potential approaches zero across diode 148. The further negative swing of the voltage at the transformer 130 secondary does not affect the relay circuit due to the diode 148.

The reverse swing of the transformer secondary is dissipated through diode 136 and the circuit comprising resistance 138 and resistance 142 and condenser 140 in parallel. The purpose of the resistance 138 and resistance 142 and condenser 140 in parallel is to limit the amount of the back-swing to measurable magnitudes on the one hand but not to lengthen its recovery time on the other. Diode 136 prevents the resistances and capacitances in parallel with the transformer secondary from loading the secondary during the initial pulse.

' Resistance 144, in parallel with condenser 146 allows discharge of the condenser between pulse applications. Resistance 142 performs the same function for condenser 140 between back-swings. The transformer 130 in addition to its main step-up function acts to DC isolate the operate control circuit from the relay preventing any false latching of the relay one way and preventing damage to the control circuitry by the relay potentials the other way.

A detector continuously connected-to line 16 will give a false indication of .operating" just after the relay releases due to thereaction of the relay coil to the interruption of current,

and may give a false indication just after the relay has operated. Accordingly it will be desirable that detection means be designed (through means having no relation to the present invention) not to detect or to ignore detections made, during a predetermined period after operation or release of the relay.

The termination of the operate" operation concludes with transistors 110 and 116 nonconducting.

The operation of the release circuit in response to a command pulse over line 200 is similar to that just described for the operate pulse and will not be described as fully since the operation of the operate and release-circuits is substantially identical, except that component values may be different due to a different desired magnitude or shape for the release pulse to the relay.

When line 200 having been quiescent and negative, to prevent conduction in transistors 210 and 216, receives a positive signal (it being assumed that the relay is then operated and contacts 10-1 are closed)of sufficient magnitude to cause conduction in transistor 210, this represents the command for the relay to release. Conduction in transistor 210 causes con duction in transistor 216 creating a surge of current in the primary and hence in the secondary of transformer 230 which is positive toward the dot and negative away from the dot. The primary surge is stepped up in the secondary creating the negative pulse at the nondotted end of the secondary of transformer 230. This negative pulse is applied through resistance 244 and condenser 246 in parallel, through diode 248 to line 14. As the potential of line 14 is carried negative by the pulse, current flow through relay 10 is reduced thereby until, as it goes below the holding minimum, the relay releases. Care is taken in circuit design that the negative swing of line 14 is not of sufficient duration or magnitude that the relay will not be operated through current flow through the relay in the opposite to the holding current direction. On the other hand the pulse from the secondary of transformer 230 is made sufficiently large that dissipation in. the secondary of transformer 11141 or through

resistances

138, 142 and condenser 140 through resistance 22 does not inhibit release of the relay by the pulse.

The above mentioned dissipation in the operate circuit during the release operation, and the previously mentioned dissipation in the release circuit during the operate operation, are merely design problems and are small disadvantages compared to the advantage of being able to connect both the operate and release circuits to the relay without the necessity of interrupter relay contacts. Such relay contacts would add to the complexity and expense of the circuit and would require extra design to avoid transient effects due to the closing and opening of relay contacts and would subject the circuit to the risk of mechanical failure.

The release circuitry has the same features as the operate. Thus the pulse emanating from the release circuitry through diode 248 is terminated not by the natural reverse swing of the transformer (which is preferably damped out for all practical purposes) but rather after a predetermined positive signal duration, by the signal on line 200 going negative. It is noted that even if a reverse swing existed the characteristics of the transformer would be preferably designed so that any reverse swing would occur after the termination of the pulse through diode 248 by the signal on line 200 going negative. Conduction is then interrupted in transistor 210, interrupting conduction in transistor 216, such interruption being rendered more gradual by the feedback from the transistor 216 through zener diode 226and diode 228. The positive swing of the nondotted end of the primary of transformer 230 causes the nondotted end of its secondary to go positive, terminating the pulse to the relay when the magnitude of the pulse emanating from the undotted end of transformer 230 secondary is more positive than line 14.

The circuitry in parallel with the secondary of transformer 230, comprising diode 246, resistance 238 condenser 140, and resistance 142 serves the same purposes as the similar circuitry in the secondary of transformer 130, with diode 246 being poled to prevent conduction in the secondary of transformer 230 when the dotted end is positive relative to the nondotted end.

Returning to the operate circuitry, terminal 112 may be operated in the use of the circuitry above described, as a part larger control system. Terminal 112 may be connected to receive a control signal having two states, a positive potential sufficient if connected to the base of transistor 110 to bias transistor 110 into conduction and an alternate potential sufficiently lower that transistor 110 will not conduct. Accordingly it will be noted that with the circuitry shown the positive signal on terminal 112 is not sufficient to turn on transistor 110 because of diode 117. On the other hand, withterminal 112 connected, a positive pulse on line 100, otherwise of sufficient magnitude to turn on transistor 110, cannot do so unless 112 is in its positive state. In such an arrangement the pulse on line 100 may be provided at regular intervals, being ineffective when terminal 112 is not in its more positive state and effective when 112 is in its more positive state. The latter condition, in combination with the positive pulse on line 100 by turning on transistor 110, creates the operate pulse for the relay.

It will be seen that terminal 114 has exactly the same effect as terminal 112 when connected to a source of control potentials, one high enough (although not connected to) bias transistor 110 into conduction, and one low enough to prevent conduction in transistor 110. When so connected the higher potential on either or both terminals 112 and 114 cannot cause an operate pulse which can only be caused by a coincidence of positive signals on terminals 112 and 114 and line 100. Thus the signal on line 114 maybe used as a redundancy check to prevent errors in operation. Thus terminal 112 is used to indicate a request for an operate pulse, terminal 114 is used to indicate thatthere is not at the same time a request for a release pulse so that when 112 indicates operate 114 indicates not release then the next pulse on line 100 causes an operate pulse. lf conflicting commands were being given, when 112 indicated operate" then 114 would be negative, i.e. release," and the relay would not be operated until 114 had altered in sign.

Similarly terminals 212 and 214 may be connected so that a release pulse may only be when 212 is sufficiently positive to indicate release" and 214 is sufficiently positive to indicate not operate."

It will be seen that when terminals 112, 114. 212. 214 are connected, then conflicting commands may not be given and the same pulses may be supplied on both line and 200 as indicated by the dotted connecting line300.

Relay contacts 17 are included toindicate that extrinsic control circuitry may command a large number of relays including four relays corresponding to'the four contacts 17. and may operate to selectively close or open contacts 17 in the circuit shown so that with such control, the circuit shown and other similar circuits affected by the same control may be controlled to only operate as described where all four contacts 17 in a circuit are closed.

It is noted that with the relay released B; may be different from B, by an amount sufficient to cause current flow (when no pulse is acting) either:

a. through elements 22, the secondary of 130, 144, 148. 14 and 10, in one polarity of B to 13,-; or

b. through

elements

10, 14, 248, 244, the secondary of 230 and 22 in the other polarity of B to B,-.

As long as the difference of B and B, is insufficient to apply currents of latching quantum'during the absence of a pulse and if the pulse producing circuitry is designed with the values of B,, B and the quiescent current in mind; then this arrangement is considered to be and the circuitry will operate in accord with the invention.

We claim:

1. Means for operating a latching electromagnetic relay connectable in series with its latching contacts and a resistance between a first potential adjacentsaid relay and a second potential adjacent said latching contact said second potential being sufficiently-different from the first, to provide the necessary holding current for said relay, through said relay said resistance and said latching contact comprising:

a step-up transformer;

having one end of its secondary connected to a potential datum and the other end connected between saidrelay and said latching contact, said resistance in series with said latching contact being connected between the connection from said transformer secondary and said second potential;

means allowing current flow from said transformer secondary to said relay only when third potential created at said other end of said transformer secondary is in the same polarity relationship to the connection point between said relay and said latching contact as said second potential bears to said first potential; and

control means for altering the state of current flow in the primary of said transformer between two states, at rates and to a degree that on alteration of said state in one a sense, a pulse of such third potential is created of dura tion and magnitude to cause latching of said relay.

2. Means as claimed in claim 1 wherein said control means for altering the state of current flow comprises a transistor connected to provide one current flow state in said transformer primary when conducting and another state when on nonconducting; and means for applying a control signal to the base of said transistor to switch said transistor on or off.

3. Means as claimed in claim 1 wherein said control means for altering the state of current flow comprises: a transistor having its power circuit connected in series with said transformer primary; means for connecting a potential across said transistor switch and primary in series, in a sense to conduct through said transistor switch, when the switch is conducting;

and means for selectively applying and removing a biasing potential to said switch to initiate and interrupt conduction.

4. Means as claimed in claim 3 wherein said transformer is wired, and said means for allowing current flow in only one direction is poled, to cause said pulse when said transistor is switched on.

5. Means for releasing a latching electromagnetic relay connectable in series with its latching contacts between a first potential adjacent said relay and a second potential adjacent said latching contact, said second potential being sufficiently different from the first to provide the necessary holding cur rent for said relay through said relay' and said latching contact and a resistance in series therewith; comprising:

a step-up transformer;

having one end of its secondary connected to a potential datum and the other end connected between said relay and said latching contact being connected;

said resistance in series with said latching'contact between the connection from said transformer secondary and said second potential;

means allowing current flow from said transformer secondary to said relay, only when'the third potential created at said other end of said secondary is in the same polarity relationship to the connection point between said relay and said latching contact as said first potential bears to said second potential; and

control means for altering the state of current flow in the primary of said transformer at rates and tea degree, that on alteration of said state in one sense, a pulse of such third potential is created ofduration and magnitude to release said relay, but of insufiicient duration and magnitude to reoperate it.

6. Means as claimed in claim.5 wherein said control means for altering the state of current flow comprises a transistor,

connected to provide one current flow state in said transformer primary when conducting and another state when nonconducting; and means for applying a control signal to the base of said transistor to switch said transistor on or off.

7. Means as claimed in claim 5 wherein said control means for altering the state of .current flow comprises: 'a transistor having its power circuit connected in series with said transformer primary; means for connecting a'potential across said transistor switch and primary in series, in a sense to conduct through said transistor switch when'the switch is conducting; and means for selectively applying and removing a biasing potential to said switch to initiate and interrupt conduction.

8. Means as claimed in claim 7 wherein said transformer is wired, and said means for allowing current flow in only one direction is poled, to cause said pulse when said transistor is' switched on.

sistor 9. Means for operating or releasing a latching electromagnetic relay connectable in series withits latching contactsand a resistance between a first potential adjacent said relay and a second potential adjacent said latching contact. said second potential being sufficiently different from the first. to provide the necessary holding current for said relay through said relay, said resistance and said latching contacts; comprising:

an operate circuit and a release circuit;

each of said circuits having a step-up transformer;

each said transformer having one end of its secondary connected to a potential datum and the other end connected between said relay and said latchingcontact; said series resistance being connected between both said transformer secondary connections and said second potential;

the connection from one transformer secondary allowing current flow only away from said transformer secondary toward said relay;

and the connection from the other transformer secondary allowing current flow only toward said transformer secondary from said relay;

control means associated with the primary of each transformer for selectively altering the state of the current flow in the primary of said transformer between two states; and stationary means for preventing substantial current flow from pulse provided at either one of said transformer secondaries in the circuit of the other of said transformer seconda es. r V i v v Ill Means as c aimedin claim? wherein saidcontrol means for altering the state of current flow comprises: a tranhaving its power circuit connected in seri e s yvith each transformer primary; means for connecting a potential across said transistor switch and primary in series, in a sense to conduct through said transistor switchwhen the latter is conducting; and means for selectively applying and removing a biasing potential to said switch to initiate and interrupt conduction therein.

ll. Means as claimed in claim 10 wherein each said transformer is wired and each said means for allowingcurrent flow in only one direction is poled to cause a pulse to pass through the respective one way current flow means associated with a transformer secondary, when the transistor associated with the primary of the same transformer is turned on.

Claims

1. Means for operating a latching electromagnetic relay connectable in series with its latching contacts and a resistance between a first potential adjacent said relay and a second potential adjacent said latching contact said second potential being sufficiently different from the first, to provide the necessary holding current for said relay, through said relay said resistance and said latching contact comprising: a step-up transformer; having one end of its secondary connected to a potential datum and the other end connected between said relay and said latching contact, said resistance in series with said latching contact being connected between the connection from said transformer secondary and said second potential; means allowing current flow from said transformer secondary to said relay only when third potential created at said other end of said transformer secondary is in the same polarity relationship to the connection point between said relay and said latching contact as said second potential bears to said first potential; and control means for altering the state of current flow in the primary of said transformer between two states, at rates and to a degree that on alteration of said state in one sense, a pulse of such third potential is created of duration and magnitude to cause latching of said relay.

3. Means as claimed in claim 1 wherein said control means for altering the state of current flow comprises: a transistor having its power circuit connected in series with said transformer primary; means for connecting a potential across said transistor switch and primary in series, in a sense to conduct through said transistor switch, when the switch is conducting; and means for selectively applying and removing a biasing potential to said switch to initiate and interrupt conduction.

5. Means for releasing a latching electromagnetic relay connectable in series with its latching contacts between a first potential adjacent said relay and a second potential adjacent said latching contact, said second potential being sufficiently different from the first to provide the necessary holding current for said relay through said relay and said latching contact and a resistance in series therewith; comprising: a step-up transformer; having one end of its secondary connected to a potential datum and the other end connected between said relay and said latching contact being connected; said resistance in series with said latching contact between the connection from said transformer secondary and said second potential; means allowing current flow from said transformer secondary to said relay, only when the third potential created at said other end of said secondary is in the same polarity relationship to the connection point between said relay and said latching contact as said first potential bears to said second potential; and control means for altering the state of current flow in the primary of said transformer at rates and to a degree, that on alteration of said state in one sense, a pulse of such third potential is created of duration and magnitude to release said relay, but of insufficient duration and magnitude to reoperate it.

6. Means as claimed in claim 5 wherein said control means for altering the state of current flow comprises a transistor connected to provide one current flow state in said transformer primary when conducting and another state when nonconducting; and means for applying a control signal to the base of said transistor to switch said transistor on or off.

7. Means as claimed in claim 5 wherein said control means for altering the state of current flow comprises: a transistor having its power circuit connected in series with said transformer primary; means for connecting a potential across said transistor switch and primary in series, in a sense to conduct through said transistor switch when the switch is conducting; and means for selectively applying and removing a biasing potential to said switch to initiate and interrupt conduction.

8. Means as claimed in claim 7 wherein said transformer is wired, and said means for allowing current flow in only one direction is poled, to cause said pulse when said transistor is switched on.

9. Means for operating or releasing a latching electromagnetic relay connectable in series with its latching contacts and a resistance between a first potential adjacent said relay and a second potential adjacent said latching contact, said second potential being sufficiently different from the first, to provide a the necessary holding current for said relay through said relay, said resistance and said latching contacts; comprising: an operate circuit and a release circuit; each of said circuits having a step-up transformer; each said transformer having one end of its secondary connected to a potential datum and the other end connected between said relay and said latching contact; said series resistance being connected between both said transformer secondary connections and said second potential; the connection from one transformer secondary allowing current flow only away from said transformer secondary toward said relay; and the connection from the other transformer secondary allowing current flow only toward said transformer secondary from said relay; control means associated with the primary of each transformer for selectively altering the state of the current flow in the primary of said transformer between two states; and stationary means for preventing substantial current flow from pulse provided at either one of said transformer secondaries in the circuit of the other said transformer secondaries.

10. Means as claimed in claim 9 wherein said control means for altering the state of current flow comprises; comprises: a transistor having its power circuit connected in series with each transformer primary; means for connecting a potential across said transistor switch and primary in series, in a sense to conduct through said transistor switch when the latter is conducting; and means for selectively applying and removing a biasing potential to said switch to initiate and interrupt conduction therein.

11. Means as claimed in claim 10 wherein each said transformer is wired and each said means for allowing current flow in only one direction is poled to cause a pulse to pass through the respective one way current flow means associated with a transformer secondary, when the transistor associated with the primary of the same transformer is turned on.