US1998436A - Signal system - Google Patents

Description

April 23, 1935. y c E, BEACH HAL 1,998,436

SIGNAL SYSTEM Filed Jan. 20, 1952 Patented Apr. 23, 1935 SIGNAL SYSTEM Clarence E. Beach, Brookline, and Foster E. Weld, Newton, Mass., assignors to The Gamewell Company, Newton, Mass., a corporation of Massachusetts Application January 20, 1932, Serial No. 587,675

12 Claims.

In signaling systems utilizing unidirectional current impulses in the normal signaling circuit and an emergency conductor carrying under certain conditions series of current impulses flowing 5 alternately in different directions, as described in the copending application of C. E. Beach, Serial No. 573,151, filed November 5, 1931, it may be desirable to employ only a minimum number of signal responsive devices and only such apparatus which is exclusively operative with unidirectional current. It is the main object of the present invention to provide such a simplified system which is nevertheless reliable and able to conform with all the essential requirements demanded from systems of this type. Another object is to provide a signaling system supplied with alternating current, and having two signal responsive devices operative only with unidirectional current, which is able to perform reliably under all important emergency conditions. Still further objects will be apparent from the following description of a concrete embodiment of my invention, by way of example, in connection with a drawing, in which:

Fig. l is a connection diagram of a fire alarm system according to the invention; and

Fig. 2 is a diagrammatical representation of its operation under emergency caused by a ground.

Referring to Fig. 1, A, B and C represent a number of signal initiating means, hereinafter referred to as alarm boxes, which are connected in series with the receiving station terminals 26, 2l by conductors 2|, 22, 23, 24 forming, with the alarm boxes, an outer signal circuit or signal loop. The alarm boxes A, B and C may be of any known type having facilities for effecting the formulation of impulses, representing de-` sired lcode signals, in a normally closed electrical circuit, together with facilities operable in every case, or only under emergency, for signaling over a ground conductor. These boxes may comprise mechanism such as that which forms the subject matter of the copending application of Clarence E. Beach, Serial No. 573,151, herenbefore referred to. The receiving station connected with the outer circuit at 26 and 21 comprises four asymmetric conductors I, 2, 3 y and 4 of suitable type, hereinafter referred to t2) as rcctiers, which are connected in a bridge circuit with terminals II, I 2, I3 and I4 intermediate the rectifiers which conduct current substantially only in the direction of the arrows of their symbols. The opposite terminals Il and I2 are connected through the secondary winding 'l of a transformer T having a primary winding 6 which is supplied through terminals 9 and IIJ from a suitable source of single phase alternating current. A resistance 8 may be inserted in series between Winding 1 and terminal I2. The terminal I2 is also connected to terminal I6 of an emergency manifesting circuit M comprising a manifesting device G, and in parallel thereto a rectifier R which conducts 'current substantially only in the direction of the arrow of its symbol. The second terminal I1 of the manifesting circuit is connected to ground, which provides a common return conductor from any grounded point of the outer circuit to the receiving station. The terminal I3 of the two other opposite terminals of the rectifier bridge is connected to a manifesting device F which is also joined to the receiving station terminal 2l. The remaining bridge terminal I4 is directly connected to terminal 26 of the receiving station.

From the foregoing it will be apparent that the current flow is unidirectional in character through the manifesting devices F and G, as well as through the signal boxes, from either end of the circuit to the other, or between either or both ends and a ground connection intermediate the ends of the circuit. Hence the magnets provided in such devicesand boxes may be of a type functioning with direct or unidirectional current ow only. It should therefore be understood that the term unidirectional" as employed throughout this specification as defining direction of potential or current flow applied to or in a given current path, is used to distinguish from alternating current, potential or current flow, as distinguishing the effect of such potential or current flow from what might be considered, under some circumstances, as the apparent potential or theoretical'potential or current flow, for example incidental to certain arrangements of asymmetric conductors.

The normal current path is effective when the signal loop is closed and ungrounded, and is as follows: During excitationof the transformer T, when the electromotive force across the Winding l is urging current flow therethrough from terminal I I toward terminal l2, current flows from Winding 1, through resistance -8 to terminal l2, thence through rectier 3 to terminal I3, thence through magnet winding of responsive device F to terminal 21, thence through conductor 24, box A, conductor 22, box B, conductor 2|, box C and conductor 23 to terminal 26, thence to terminal Ill, through rectifier 4 and terminal II to the other end of winding 1.

At an instant when current ow through winding 1 is" urged from terminal I2 toward terminal II, current flows from said winding to terminal II, thence through rectier 2 to terminal I3, thence in the current path just traced through the outside loop to terminals 26 and I4, through rectifier I to terminal I2, thence through resistance 8 to the other end of windingl 1.

From the foregoing it will be apparent that under this condition there is full Wave rectication of the alternating current which excites the Winding 1, and that the resultant current flow in the outside signal loop and through the winding of manifesting device F is unidirectional.

Furthermore, due to the inductance of the current path just referred to, and more particularly of the magnet Winding of device F, as well as any other magnet windings which may be included in that path (as in the boxes A, B and C), current flow through all such magnet windings is maintained in normal direction during intervals of decreased and zero potential across the winding 1, because of the parallel paths for what may be termed a circulating current whichA are provided from terminal I4 to terminal I3; one such path including the rectiers I and 3 and the other path the rectifiers 4 and 2.

The flow of current in the circulating current paths just referred to is believed to arise in a manner which may be described as follows: At times when the flow of exciting current in the electromagnet windings of any current path is increasing, a counter-electromotive force is built up due to the inductance of such path. After reaching a maximum, when such current flow starts to decline, such inductance induces a voltage which tends to retard the decline of exciting current strength; and although such tendency would be substantially overcome were there no current path through which flow could be maintained during change in the electromotive force of the alternating current source (as the secondary transformer winding 1) provision is thus made for current flow responsive to such inductively produced electromotive force through low resistance paths which are independent of the current source. It will thus be seen that the flow of circulating current thus permitted serves to sustain, to a substantial degree, the attractive force of the magnet structures.

In the event of interruption of the normally closed and ungrounded loop current path just described, as from the operation of one of the boxes A, B, C, the magnet of the manifesting device F is deenergized. It is therefore evident that the manifesting device F may be actuated by breaking and closing the outside signal loop in accordance with'a desired code signal. However, so long as the signal loop remains ungrounded, the magnet of manifesting device G remains deenergized, and that device will therefore not respond to signals formulated by merely breaking and closing the the normally conditioned, ungrounded outside signal loop. Should the formulation of a code signal be effected by 'alternately closing and breaking a connection between the signal loop and the ground, the magnet of the manifesting device G is energized responsive to each closure and deenergized responsive to each break; the current paths effective during closures being as follows:

Assuming that the signal looplis grounded at box C incidental to the formulation of the code signal thereof, but that the normal current path through said loop is not interrupted or grounded elsewhere in the loop, as at any other box, a supplemental path is rendered effective upon each closure of such ground connection, in parallel with the normal path through the portion of the outside loop at one side of the box C during excitation of the winding 1 in one direction, and rendered effective in parallel with the normal path through the other side of the loop during excitation of the winding 1 in the opposite direction.

Thus, during excitation of the winding 1 in a direction urging current flow therethrough toward terminal I2, a path is provided from said terminal I2 to terminal I6, thence through winding of manifesting device G to terminal I1 (but a negligible amount of current leaking around device G through rectifier R) through the earth and ground connection K to station C. It is evident that the path just traced is in parallel with the normal path from terminal I2 to box C through rectifier 3, magnet of manifesting device F, and conductors 24, 22, 2I and boxes A and B.

correspondingly, during excitation of the winding 1 in a direction urging current flow therethrough toward terminal I I, a path is provided from box C, through ground connection K and the earth to terminal I1, thence through rectifier R and terminal I6 to terminal I2. It is evident that the path just described is in parallel with the normal path which is effective during current flow in the direction stated through wind- Y for current flow induced by the inductance of* the electromagnet winding of device F, in a man# ner and with a result similar to that previously described in connection with the energization of the normal metallic path; and, correspondingly, when manifesting device G is acting in response to a signal, rectifier R not only serves to shunt one direction of current ow around said device but also provides a circulating path for current induced by the inductance of the electromagnet winding of said device.

'Ihe presence of these paths causes a distinct increase in the mean effective current output from the winding 1, besides rendering the unidirectional current flow representative of the succeeding half cycles of the alternating current source disproportionally effective in the respective portions of the outside loop situated at one side and the other of box C. Thus, during excitation of winding 1 in a direction urging current flow therethrough from terminal I2 toward terminal II, the strength of current flow through instrument F is the sum of the strengths of the current flows through the parallel paths then provided through the ground and rectifier R and through conductor 23 and rectifier 4 to terminal II. During the next, half cycle of the exciting circuit the flow through the winding of the magnet of device F consists only of the remainder of the current flow through conductor 23, after deducting that portion thereof which flows from terminal I2, through terminal I6, magnet winding of device G, and through the earth to station C.

In this connection it should be noted that the resistance of the current path from terminal I2 to terminal Il through manifesting device G and the earth, is much lower than the resistance from terminal I2 through rectiler 3, magnet of device F and the line conductors to the active station. In other words, the current flow through the earth is distinctly increased because the full electromotive force developed in the winding I (less whatever drop there is through resistance 8) is applied to the ground path so as to alternately shunt rectifiers 3 and 4 during succeeding half cycles.

Furthermore. due to the provision of a current path for circulating current around the magnet winding of device G, and the high values to which current flow rises in such Winding during the half cycles which are effective for the energization of such magnet, the mean effective energization thereof is sufficient to assure responsiveness to code signaling impulses 'during which the ground connection is effective, which response is as dependable as that of the device F to breaks and closures of the normal ungrounded signaling current path.

It should be further noted that the circuit arrangement here provided assures dependable response of the device G to grounding of the outside loop irrespective of the fact that the location of the point at which the ground connection is applied may cause inclusion of practically the entire resistance of the loop between such ground connection and the terminal 2l or the terminal 26, notwithstanding substantial varia- `tion in the total resistance of such outside loop.

Should a persisting ground connection or leak develop, for example at d, boxes situated in the portion of the outside loop between said ground leak and the manifesting device F will be responded to by that device, but would not be responded to by manifesting device G; while boxes situated between such leak and terminal 2B would be responded to by manifesting device G, but not by manifesting device F.

Thus it is evident that during the continuance of a comparatively low resistance ground leak at d, operation of the box A causes breaks and closures of the current path through manifesting device F, so that said device responds thereto; but does not cause interruptions of current flow through manifesting device G, because such current, passing from terminals I2 and I'I through the earth to ground d returns to winding l, through conductors 2|, 23, terminals 26 and Ill, and rectifier 4. v

Correspondingly, operation of either box B or box C causes under such conditions interruptions of the current path last referred to, thereby causing response of manifesting device G, but not interrupt-ing current flow through manifesting device F.

The alternative current paths effective while there is a ground leak such as `iust referred to, may better be visualized by reference to Fig.4 2, in which the solid and dotted arrows indicate the paths through which current flow is effective during succeeding half cycles; the solid arrows indicating the direction of current ow at an instant when the excitation of winding 'I is in the direction from terminal II toward terminal I2 and the dotted arrows indicating the paths effective during excitation in the opposite direction. It will thus be seen that the solid arrow 3|, associated with the lower end of winding I, indicates a branching of current ow at terminal I2, one portion of such flow passing to the right through rectifier 3, terminal i3, winding F, conductor 24, and box A to locality of ground leak d; while the other branch continues downwardly from terminal I2 through winding G and the earth to the circuit loop at the point of leak d, where the solid arrows from the two branches converge, passing through boxes B and C to terminal I4, thence through rectifier 4 and terminal II to the other end of winding l.

It will be further seen that the dotted arrow 32 associated with the upper end of winding l leads to other like arrows indicating a path from terminal I I, through rectifier 2, terminal I3, winding F, conductor 24 and box A to the ground leak d, where there is indicated a branching of current flow, one portion passing upward through the earth and the other rectifier R (around the winding of device G) to terminal I2, while the other branch continues through conductor 23 to terminal I4 through rectifier I, where the dotted arrows from the two branches converge and lead to the other end of winding 32.

It is evident from the foregoing description that during a ground leakage of substantial extent signals from any of the boxes of the loop may be received on one of the two manifesting devices, depending on the relative positions of ground fault and signaling box.

Should the signal loop be broken at any one place, the operation of any box causes response of one or the other of manifesting dvices F and G, in the absence of ground leakage'of serious proportions in the portion of the circuit between the active box and the unbroken conductor to the central ofce. Should the signal loop be broken at point h, as indicated in Fig. 1, operation of any of the boxes A, B, C, causes manifesting device F to respond, provided that such box is of a type which establishes a ground connection during each`code signaling impulse irrespective of circuit conditions, or of a type in which a noninterference magnet acts responsive to the broken line condition to establish a ground connection effective during signaling impulses as, for example, boxes constructed in accordance with United States Patents 553,838 to F. W. Cole, dated February 4th, 1896, and 1,210,398 to C. E. Beach, dated January 2nd, 1917.

If, on the other hand, conductor 24 is broken, and one of the boxes of a type just referred to is operated, it is evident that the code signaling impulses of such boxes cause response of manifesting device G. If conductor 22 is broken, the boxes (such as box A) connected by an unbroken wire from such break to manifesting device F will be responded to by said device, and the boxes (such as boxes B and C) connected by an unbroken wire with terminal 26 will be responded to by manifesting device G.

Should the two boxes, acting as hereinbefore more fully described, concurrently formulate their respective code signals at respective sides of a circuit break, manifesting device F will respond to the signal of one of such boxes and manifesting device G will respond to the signal of the other of such boxes.

As pointed out hereinbefore, the terminal I2 is also associated with the ground through the connection M. There is thus provided a current path or common return conductor through which emergency connections may be established with various portions of the outer circuit which completes the normal signaling current path. The terminal I 3 of the two other opposite terminals of the rectified bridge is connected to a manifesting device F which is also joined to the receiving station terminal 21. The remaining bridge terminal I4 is directly connected to terminal 26 of the receiving station.

Should a signal be formulated by making and breaking between terminal I2 and a point on the outer circuit to which there is an effective current path through manifesting device F from terminal i3, at a time when the normal outer current path is interrupted between such point and terminal I4, said device F will respond to such signal. For the purpose of assuring correct response of manifesting device F to signals formulated within the current path just indicated, it is evident that no more will be needed than to breaking between a point on the outer circuit from which there is an effective current path to terminal I4' at a time when the normal current path from such point through manifesting device F to terminal I3 is broken, it is evident that manifesting device F would not respond to such signal. Manifesting device G is therefore associated with the connection M.

The rectifier R is so connected in parallel with manifesting device G that current flow between terminal I2 and the ground is opposed by said rectifier, when in the direction representative of half waves to which manifesting device F is not responsive, so as to divert substantially the establish a ground connection between terminal entire current flow incidental to such half waves I2 and a suitable portion of the outer circuit.

In this relation it should be observed that in the event of the establishment of a connection (as through the ground) between terminal I2 and any point in the unbroken outside current path (as, for example, at ground connection d), the current now through such ground connection will be alternating in character in that one component will be representative of the half wave which passes from one end of transformer secondary winding 1, to terminal II, through rectifier 2, terminal I3, manifesting device F, terminal 21, conductor 24 to ground connection d, where the current flow of such component will divide and one portion will pass through ground connection d, connection M to terminal I2 and transformer secondary winding 1, while the other portion will pass through conductors 2| and 23, terminals 26 and I4, and rectifier I to terminal I2, where the two portions will again combine and proceed to the other end of transformer secondary 1. During the next half cycle, current will ow from transformer secondary winding 1 to terminal I2, where it Will divide and one portion will flow through rectifier 3, terminal I3, manifesting device F, terminal21, and conductor 24 lto ground connection d, and the other portion will flow through connection M, the ground and connection d to conductor 22, at which point both portions will unite and from thence proceed through conductors 22, 2I and 23 to terminals 26 and I4, thence through rectifier 4 and terminal II to the other end of transformer secondary winding 1.

From the foregoing it will be apparent that, during'one-half cycle, the current flow through connections M and d, and through the ground, will be in one direction and, during the next half cycle, in the oposite direction, In other words, the current flow through connection M will have two components, one representative of current iiow which is passing through manifesting device F and the other representative of current flow which does not pass through this device.

It is evident that the component of current flow which passes through manifesting device F will be responded to by said device, so that if such current flow is alternately interrupted and established for the formulation of a signal, manifesting device F will respond to such signal. On the other hand, it is evident that the other component of the current flow through connection M is not responded to by manifesting device F, so that if such current ow is alternately interrupted and established for the purpose of formulating a signal, manifesting device F will not respond to such signal and such signal will therefore be lost unless some other manifesting device is so connected as to be responsive thereto. Thus, if a signal should be formulated by making and through said manifesting device G; while pernitting current flow in the direction which is representative to the half waves to which manifesting device F is responsive, to freely pass through said rectified R, so as to render manifesting device G unresponsive thereto.

Because of the arrangement just described, response to signals is assured under conditions as follows:

1. When the outer circuit is closed, and ungrounded, formulation of a code signal by alternately breaking and closing the current path through said circuit will be responded to by manifesting device F, inasmuch as the entire current flow rendered effective during closures of the current path then effective includes this device.

2. If the outside current path is grounded (as for example, at d) a code signal may be formulated by alternately breaking and closing the current path between such ground connection and terminal I3 (as, for example, at station A) and manifesting device F will be responsive thereto, inasmuch as the half wave component of Vthe alternating current flow through the ground, and through connections M and d which is affected by the formulation of such signal is that which controls manifesting device F; if, on the other hand, such signal formulation occurs in the portion of the outside circuit between such ground connection and terminal I4 (as, for example, at stations B or C) the half waves affected by such signal formulation will be those to which manifesting device G is responsive and said device will therefore respond thereto.

3. Should the outside circuit be broken (as, for example, by rupture of conductor 22) formulation of a code signal by alternately closing and breaking a connection between ground and the portion of the outside circuit which remains in effective connection with terminal I3 will cause response of manifesting device F; and correspondingly, signal formulation between the ground and a portion of the outside circuit which remains in effective connection with terminal I4 will cause response of manifesting device G.

4. If the outside circuit is either broken or grounded at any point (as, for example, ata point along conductor 22) code signals may be concurrently formulated at respective sides of such break or ground (as, for example, at stations A and B) and manifesting device F will completely and correctly respond to one of said signals and manifesting device G will completely and correctly respond to the other of said signals, because the arrangement is such that manifesting devices F and G are responsive to the formulation of signals at respective sides and only at such respective sides of the break or ground.

5. If the outside circuit remains unbroken,

but a signal is formulated by alternately closing and breaking between some point on the outside circuit and the ground, manifesting device G will respond to such signal, inasmuch as there will be alternating current ow through the connection M during each such closure and the manifesting device G responds to one of the components or half waves of each of the cycles of alternating current ow which occurs through the connection M during each such closure; but

manifesting device F will not respond, inasmuch as the current flow therethrough will not be interrupted because of the formulation of such a signal.

It should be noted that the relative connections of the manifesting device G and rectier R as shown and hereinbefore described are essential for attainment of the foregoing functional effects; thus, for example, if the controlling electromagnet of the manifesting device G was merely of a type which rendered it responsive to alternating current, or was so rendered responsive to alternating current through association with the connection M through a socalled bridge rectifier" such manifesting device G would be rendered responsive to .all current flow through the ground connection. In such an event, if signals were being received from stations at respective sides of a break or ground, while manifesting device F might correctly respond to one of such signals, a manifesting device which was responsive to current flow in both directions through the ground connection would respond to both of such signals, so that its action would not be truly or independently representative of either signal, but would present a confused combination of the two. Furthermore, inasmuch as the controlling electromagnet of manifesting device G would then be included in the current path upon which manifesting device F was dependent, if the resistance of the ground connection was suiiciently high, the current ow might be so reduced as to destroy the dependability of the response of manifesting device F to such a signal. Under like conditions, a signaling system arranged in accordance with the present invention causes dependably correct response of manifesting device F, as the current path upon which its response is dependent is shunted around manifesting device G through rectifier R.

It should furthermore be understood that although inclusion of a manifesting device in the current path between terminal Hl and the outer circuit would provide for independent response to concurrent signals from respective sides of a. break or ground, such an instrument would not respond to the formulation of a signal effected without breaking the outside circuit, bymerely closing and breaking a connection between such circuit and the ground.

From the foregoing it is apparent that the new circuit operates successfully with boxes having non-interference and succession effects, with short circuits bridging any number of boxes and not only under the faulty conditions which have been expressly discussed but also under more or less similar troubles or combinations thereof. For instance emergency signaling is possible irrespective of the fact whether a fault occurs upon the line between the alarm boxes or within the boxes or upon the lines leading from the boxes to the receiving station. Signaling is also possible when there are two or more breaks in the signaling loop, two or more grounds in the sigl' nalmg loop, one or more breaks and one or more grounds, or when the circuit is broken in one or vmore places and the active box (or the portion of the circuit including it) is short-circuited or shunted out; in fact, signaling is possible under almost any defective line condition, with the exception of a few so-called electrically hopeless cases wherein boxes are situated in the circuit between two breaks, between a break and a low resistance ground, between two low resistance grounds, or when the active box or the portion of the signal loop in which it is connected is short-circuited and the loop also has a low resistance ground leak.

It will be evident that our invention is useful not only when `employed with grounding signal sending devices in the signal path or loop as above described, but that it can be used, for example, for indicating any ground connection of a conventional signal loop, any connection of the loop with the common return conductor being indicated by instrument G, which is then supplied with single wave unidirectional current smoothed out due to the presence of the above described circulating path exclusive of the current source.

In the .embodiment above described the asymmetric valve R may be reversed so that, instead of passing current from the ground towards the rectier bridge, it passes current from the bridge towards the ground. If the rectifier R is thus reversed, the rectlers l, 2, 3, l of the current supply bridge should also be reversed in order to maintain proper operation.

It should be understood that the present djsclosure is for the purpose of illustration only and that this invention includes all modications and equivalents which fall within the scopeof the appended claims.

We claim:

1. An electric signaling system comprising a signaling path, an associated conductor, means for applying a substantially unidirectional electromotive force between the endsv of said path and for applying the half waves of one direction of an alternating electromotive force between said conductor and one end of said path and the half waves of the 4other direction of said alternating electromotive force between said conductor and the other end of said path, means for formulating code signals within said path and between said path and said conductor, a signal device responsively associated with said one of said ends, signal manifesting means associated with said conductor and means rendering said manifesting means responsive only to current flow in the direction of the half waves applied between said conductor and said other one of said ends.

2. An electric signaling system comprising a signaling path, an associated conductor, means for applying a substantially unidirectional electromotive force between the ends of said path and for applying the half waves of one direction of an alternating electromotive force between said conductor and one end of said path and the half waves of the other direction of said alternating electromotive force between said conductor and the other end of said path, means for altering conductive characteristics within said path and between said path and said conductor, a signal device responsively associated with said one end of said path, signal manifesting means associated with said conductor, and means rendering said manifesting means responsive only to current ow in the direction of the half waves applied between said conductor and said other end of said path.

3. An electric signaling system comprising a rectifier bridge having terminalsfor alternating current input and for unidirectional current output, three circuit conductors one of which is connected to one of said input terminals and the other two of which are connected to said output terminals, a series of unidirectional impulses in a given direction resulting in, and from connection of, said first conductor with one of said two conductors and a like series of impulses in the opposite direction resulting in, and from connection of, said first conductor with the other of said two conductors, a signal device responsively associated with said other of said two conductors, signal manifesting means associated with said first conductor and means rendering said manifesting means responsive only to impulsesl of said first series.

4. An electric signaling system comprising a rectifier bridge having terminals for alternating current input and for unidirectionalcurrent output, three circuit conductors one of which is connected to one of said input terminals and the other two of which are connected to said output terminals, a series of unidirectional impulses in a given direction resulting in, and from connection of, said rst conductor with one of said two conductors and a like series of impulses in the opposite direction resulting in, and from connection of, said rst conductor with the other of said two conductors, means forv formulating code signais by effecting alterations in the conductive relationships between said conductors, a signal device responsively associated with said other of said two conductors, signal manifesting means associated with said first conductor, and means rendering said manifesting means responsive only to impulses of said first series.

5. An electric signaling system comprising a rectifier bridge having two main terminals and an intermediate terminal and supplying two series of alternate impulses of unidirectional electromotive forces between one of said main terminals and said intermediate terminal and between said intermediate and the other main terminal, respectively, a normally closed signaling current path involving signal formulating facilities and connected to said main terminals, a manifesting device serially included in said path, a conductor through which connections may be established between said intermediate terminal and various portions of said path, signal manifesting means serially connected in said conductor, and an asymmetric conducting path in parallel with and for by-passing around said manifesting means substantially all current flow of one impulse series whereby said manifesting means is rendered responsive only to current flow of the other impulse series.

6. An electric signaling system comprising a signaling current path involving a manifesting device, a conductor including manifesting means, means for formulating signal impulses within said path and between said path and said conductor, means for applying a unidirectional electromotive force between the ends of said path and for applying the half waves of one direction of an alternating electromotive force between said conductor and one end of said path and the half waves of the other direction of said alternating electromotive force between said conductor and the other end of said path, and an asymmetric conducting path in parallel with and for lay-passing around said manifesting means substantially all current flow of the half waves of one direction. whereby said manifesting means is rendered responsive only to connections between said conductor and said signaling path which affect a circuit including a predetermined one of said signaling path ends.

7. An electric signaling system comprising a signaling current path serially including a manifesting device and involving signal formulating facilities, a conductor including manifesting means through which connections may be established with a point of said path, means for applying through said conductor alternating current whose half waves of respective directions impress unidirectional electromotive forces upon component circuits including portions of said path on respective sides of said point, and an asymmetric conducting path in parallel with and for by-passing around said manifesting means substantially all current flow of half waves of one direction, whereby said manifesting means is rendered responsive only to connections between said conductor and said signaling path which are effective through a predetermined one of said component circuits.

8. A signal system comprising an alternating current source, a signaling current loop having two terminals and containing therein provisions for interrupting said loop, a conductor and provisions whereby it may be connected to a portion of said loop, means connected to said terminals supplying thereto a substantially unidirectional electromotive force derived from succeeding half waves of said source and supplying the electromotive forces of alternate half waves of said source between a point of saidconductor and respective ones of said terminals, signal manifesting means in said conductor between said provisions and said point and responsive only to current resultant from said electromotive force supplied between said point and one of said terminals, and signal manifesting means in said loop near the other one of said terminals.

9. A signaling system comprising analternating current source, a signaling loop having two terminals, a conductor and provisions whereby it may be connected to a portion of said loop, a full wave rectifier bridge having two input terminals and two output terminals, one input terminal being connected to a terminal of said source, the second input terminal being connected to the other terminal of said source and to a point of said conductor, and said output terminals being connected to respective ones of said loop terminals, said bridge providing circulating current paths exclusive of said source between either one of said loopterminals and said point of said conductor, signal responsive means in said conductor between said provisions and said point, and an electric valve in parallel with said manifesting means for bypassing around said manifesting means substantially all current flowing in said conductor in one direction, said manifesting means being rendered responsive only to current flowing in said conductor in the other direction, in a circuit including a predetermined one of said circulating paths.

10. A signaling system comprising an alternating current source, a signaling loop having two terminals and containing therein provisions for interrupting said loop, a conductor and provisions whereby it may be connected to a portion of said loop, a full wave rectifier bridge having two input terminals and two output terminals, one input terminal being connected to a terminal of said source, the second input terminal being connected to the other terminal of said source and to a point of said conductor, and said output terminals being connected to respective ones of said loop terminals, said bridge providing circulating current paths exclusive of said source between either one of said loop terminals and said point of said conductor, signal manifesting means in said conductor between said provisions and said point, and an electric valve in parallel with said manifesting means for bypassing around said manifesting means substantially all current flowing in said conductor in one direction, said manifesting means being rendered responsive only to current owing in said conductor in the other direction, in a circuit including a predetermined one of said circulating paths.

11. Central oice equipment for a signaling system of the type having a signaling current path and a ground or common return conductor at times connected to said path, comprising terminals for the respective ends of said path and a third terminal for said conductor, an alternating current source, connections including unidirectional conducting means between said source and respective ones of said terminals, the connections to two of said terminals respectively being so ap-` plied to said source through said unidirectional conducting means as to urge current'ow of one series of half waves between such two terminals passing in a certain direction through a predetermined one of said connections, and the remaining connection being so applied to said source through said unidirectional conducting means as to urge current iiow of the other series of half waves between such connection and said predetermined one of the rst named two connections,

said current ow passing through said predetermined one of said connections in the opposite direction, signal manifesting means responsive to current flow in respective ones of said rst named two connections, and means for rendering the manifesting means of said predetermined one of said rst named two connections responsive lto current flow therein only in said opposite direc-l tion.

l2. Central oice equipment for use in signaling systems of the type where a signaling current path and a ground or common return conductor may at times be connected, comprising terminals for the respective ends of said path and a third terminal for said conductor, a source of alternating current, connections including unidirectional conducting means between said source and said terminals, the connections to one of said signaling path terminals and to said third terminal, respectively, being so applied to saidsource as to urge current flow of one-half wave series therebetween passing in a certain direction through said third terminal connection, and the remaining connection so applied to said current source as to urge current iow of the other series of half waves between said remaining connections and said third terminal connection, said current flow passing through said third terminal connection in the opposite direction, signal manifesting means responsive to current flow in said rst and second named connections, and means for rendering the manifesting means of said second connection responsive to current flow therein only in said opposite direction. v

CLARENCE E. BEACH.

FOSTER E. WELD.

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