US 2347505 A
Description (OCR text may contain errors)
April 25, 1944.
c. s. RHoADs PHANTOM MAGNETO TELEPHOE SYSTEM Filed May 21, 194s 2 sheets-sheet 1 SNL mvENToR BY Cllwaas ,ATTORNEY April 25, 1944. c. Vs. Rl-loADus 2,347,505
PHANTOM MAGNET@ TELEPHONE SYSTEM Filed .May 21, 1943 2 Sheets-Sheet 2 lNVE-NTOR ATTORNEY Patented Apr. 25, 1944 UNITED STAT E S T NT FFECE PHANTOM MAGNETO TELEPHONE SYSTEM Applcation lJlay 21, 1943, Serial No. 487,891
This invention relates to telephone systems, and more particularly to phantom circuits for telephone systems. Still more particularly this invention relates to arrangements for providing a phantom circuit from two telephone trunk circuits, the phantom circuit being equipped with a magneto. set for auxiliary signaling.
A community dial ofce, generally unattended, is often connected to a master or operator oiiice, generally attended, by a number of trunk circuits to enable subscribers in the area of the community dial ofce to communicate with the operator or subscribers in the areaV of the master or operator omcey and, via that office, with operators or subscribers at more remote points. The apparatus at the community dial oihce is usually arranged so that a subscriber may automatically select one ci the trunk circuits by properly operating his dial set, It may happen, however., that the selectors or switches that control the selection and seizurev of one of the trunks are busy or that all of the trunks are busy, in which case the operation of the dial set to establish a connection to the operator at the master oliice or to any of they subscribers reached via that oiiice will be of no avail. Such a situation may be quite serious, especially during periods of emergency.
Accordingly it is an object of this invention to provide a phantom circuit by connection oi apparatus to two telephone trunk circuits to enable fr'.
a subscriber to signal either an operator at the master ofce or a subscriber in the area of "le master ofce when all selectors or switches or trunks are busy. The phantom circuit of this invention involves additional equipment includp ing a magneto telephone set arranged so that the operation of the magneto generator ofthe set will not interfere with signaling over the trunk circuits or cause false operation of the trunk circuits.
This invention will be better understood from the more detailed description hereinafter 'following when read in connection with the accompa nying drawings, in which Figure l illustrates a master ciice and a community dial cfce interconnected by trunk circuits and provided with. a magneto telephone set inserted in a phantom circuit for use with the trunk circuits side circuits, and Fig. 2 shows schematically switciiing contacts controlled by the magneto generator of the magneto telephone set and arranged to prevent interference with and false operation of the equipment of the trunk circuits. A
Referring to Fig. 1 of the drawings, two trunk circuits TK1 and TKz of a group of similar trunk circuits are shown interconnecting a community dial olce CDO', usually unattended, and a master oiiice MO at which one or more operators may be in attendance. Each of these trunk circuits TKi and IKz may be employed for two-way signaling in a well known manner between the two offices and between subscribers connected to the two oices. A magneto telephone set MS may also be connected tothe community dial cnice CDO and this set may be located in the areav or" the community dial oliice in the saine manner that the subscribers telephone setsV S81 and S82, for example, are so` located. The magneto set MS is connected tov the. trunk TK1 over parallel paths which include condensers C1 and C2 extend-ing tothe upper and lower portions of the primary windings of the transformer or repeating coil RC1. The magneto set MS is likewise connected to the trunk TX2 by two parallel paths including condensers C3 and C4 which extend to theY upper and lower portions of the primary windings `of the` repeating coil or transformer RC2. The upper and lower windings of the battery and ground relay BGi associated with trunk TK1 are connected to ground and battery B1, respectively, the paths to ground and battery including contacts ll and l, respectively, of the switching device K. Similarly the upper and lower `windings of the battery and groundrelay BGz associated with trunk Trie are connected to battery B2 and ground through the contacts I3 and it of the switching device K. When the switching device l is operated, the contacts ll, I2, I3 and it will .be opened, in which case the 'upper and lower windings of relay B Gl will be connected to ground and battery Bi through the 'rectifying elements RKl and EKL respectively,
and the upper and lower windings of relay BG2 will be similarly connected to battery E2 and ground throughthe rectiiying elements Rls and RKL, respectively, The switching device K may be hand-operated or it may, `if desired, be controlled by the operation of the magneto generator MG of the magneto set MS, as will be described more particularly with respect to Fig. 2. However, whenever the device 'K is operated it controls. the addition of the rectiers R311 to RKi to the relays BGl and BGZ of the two trunk circuits TKl and 1K2. As will be explained hereinafter, these rectiiiers rectify the current of the magneto generator MG, enabling the rectiied current to flow through the windings of the relays EGi and BGrz unidirectionally and thereby prevent the release or chatter of these relays. The rectiiiers therefore prevent false operation of the switching apparatus controlled by these relays.
At the master oice MO the upper and lower primary windings of the repeating coil or transformer RC3 are connected by the parallel condensers C5 and Cs to one side of a jack Jo which may terminate the phantom circuit and the upper and lower primary windings of the repeating coil of transformer RC4 are similarly connected by condensers C7 and Ca, respectively, to the other side of the jack Jn. These condensers are inserted in the circuit; so that the alternating current produced by the magneto generator MG of the magneto Set MS may alone cause the ringdown relay Ro to be operated. The relay R0 will be employed to light a lamp Lo to signal the operator at the master oce for auxiliary or emergency purposes. The operation of the phantom circuit of this invention will be described somewhat more fully hereinafter.
The trunk circuits TK1 and TKz and the apparatus associated with these trunk circuits are of the usual type and they will be described only briey. Whenever the subscriber having the telephone set SS1 connected to the community dial ofllce CDO desires to communicate with the operator at the master oice MO, he will operate his dial set in the usual way. This will cause the selector or switching apparatus SW1 to nd an idle trunk such as TK1 and seize the trunk to complete a path to the master oice. When the trunk TK1 is seized, current will flow from the battery Ba through the lower winding of relay BS1, the lower secondary winding of repeating coil RC1, through the apparatus SW1 to the telephone set SS1, and back over the upper conductor extending to the telephone set SS1, through the apparatus SW1 and then through the upper secondary winding of the repeating coil RC1, the upper winding of relay BS1 and ground. As relay BS1 operates it establishes an obvious circuit for the operation of the relay BR1. When relay BB1 operates, its two armatures reverse the connections to the conductors of trunk TK1, whereupon current will flow from battery B1 over a .circuit including contacts I2 of the switching device K, the lower winding of relay BG1, the lower primary winding of the repeating coil RC1, the lower armature and make contact of relay BB1, the upper conductor of trunk TK1, the'upper primary winding of repeating coil RC3, the windings of relay P1, the lower primary winding of repeating coil RC3, the contacts I1 of the dial jack DJ1, the lower conductor of trunk TK1, the upper armature and make contact of relay BR1, the upper primary winding of repeating coil RC1, the upper winding of relay BG1, contacts H of the switching device K and ground. The flow of this current through the windings of the polarized relay P1 is now in such a direction as to cause the relay P1 to become operated. As relay P1 becomes operated it completes a circuit to illuminate lamp L1, the circuit including the armature and make contact of relay P1, the lamp L1, the armature and back contact of relay R1, battery B4 and ground. The illumination of the lamp L1 will attract the operators attention and she will therefore insert her plug PL into the jack J1 which is associated with the lamp L1 and trunk TK1 to answer the call.
Upon the insertion of plug PL into jack J1 a circuit will be established to operate relay R1, this circuit including the upper contact I9 0f jack J1, the winding of relay R1 and ground. When relay R1 operates it opens the circuit of lamp L1, thereby extinguishing the lamp L1. The operators set will then be connected to the telephone set SS1, over trunk TK1 to allow the operator and the subscriber to speak to each other. A subscribers set such as SS1 may likewise be connected to the operator at the master office through the equipment at the community dial oice CDO and over trunk 'IKz in the manner already described in respect to telephone subscribers set SS1.
The dial jacks DJ1 and DJz are shown connected to the trunks TK1 and TKz, respectively. The operator may connect her dial set to either of these jacks for connecting the trunk TK1, for example, to any one of the various subscribers sets such as SS1, SSz, etc. When the dial set is connected to the jack DJ1, the dial pulses will be transmitted overthe trunk TK1 to operate the relay BG1 in accordance with the pulses produced by the dial, whereupon the armature of the relay BG1 will close its contact a number of times to control switching apparatus for selecting any desired one of the various telephone circuits such as SS1, SSz, etc. The switching apparatus has not been shown in detail as it is not required for an understanding of the invention.
The magneto set MS may be located on the same premises as either the sub-set SS1 or the sub-set SSz or at a different location. Whenever the subscribers set SS1, for example, receives a busy signal after dialing the operator or any of the subscribers in the areas of the two oices, the magneto generator MG may then be operated by hand for establishing a phantom circuit to the operator at the master office to attract her attention. Such a busy condition is not infrequent for it may arise Whenever the selectors or switches such as SW1 and SW2 are busy or when the trunks TK1 and TKz are busy. The hand generator MG will transmit an alternating current over the :phantom circuit proy vided by the trunk circuits TK1 and TKz to operate the relay Ro at the master oilice, as already stated. The interconnectedcircuit will include one path over the parallel condensers C1 and C2 and through the upper and lower primary windings of the repeating coil RC1, the two conductors of the trunk TK1, the two primary windings of repeating coil RC3, the .parallel condensers C5 and Cs associated with the trunk TK1, the thermistor TH, the winding of relay Ro, the contact 28 of jack Jo, and then back over parallel circuits including condensers C7 and Cs associated with trunk TX2, the upper and lower primary windings of repeating coil RC4, the two conductors of trunk TKz, the two primary windings of the repeating coil RC2, the parallel condensers C3 and C4 to the generator MG. This alternating current will cause relay Ro to operate as already stated and complete an obvious circuit to illuminate lamp Lo. The operators attention will be attracted by lamp L0 and upon the insertion of her plug PL into jack Jo to answer the call, the lamp L0 will be extinguished.
When plugPL is inserted into jack Jo the operators telephone set will be connected to the magneto set MS to enable the operator and the subscriber controlling the magneto generator MG to talk with each other. The talking path at the master office will include the condensers C5 and Cs which are connected to trunk TK1, and the condensers C1 and Cs which are con- TK1 and TKz.
This undesirable condition, however, may be 'y nected to the trunk TKz. The talking path at the community dial -omce -CDO will include the condensers C1 and C2, which are connected to trunk TK1, and condensers C3 and C4 which are connected to trunk TKz. The telephone transmitter and receiver of the magneto set MS will be connected to this phantom circuit when the telephone receiver is removed from its switchhook SH.
It is noted that the upper terminal lof the magneto generator MG is connected through parallel paths including condensers C1 and C2 and the upper and lower windings of relay BG1 to ground and battery B1, respectively, and that the lower terminal of magneto generator MG is connected to the upper and lower windings of relay BG2 and battery B2 and ground, respectively. The alternating current of magneto generator MG may therefore traverse the windings of -both relays BG1 and BG1, and cause their false operation. These relays will alternately open and close their respective make contacts in response to the generated current. As the make contacts of these relays are closed, the existing connections (not shown) established through the armatures of these relays to trunks TK1 and TK2 will be opened and hence the trunks TK1 vand TKz may be released. Hence existing communication over trunks TK1 and TKz will be terminated. In other words, the operation of the magneto generator MG may cause the relays BR1 and BRz to chatter and thereby interfere with talking or signaling over the two trunks Such a condition is undesirable.
overcome by simply operating switching device K.
When the switching device K is operated, it will insert rectifying elements into the circuits ci the windings of relays BG1 and BGz. With the device K operated, contacts Il and I2 will be opened and rectifiers RK1 and RKZ will be connected between the upper and lower windings of relay BG1 and ground and battery B1,
respectively. Similarly contacts I3 and IA. will".
be opened, interposing rectiiiers RKg and RK; in the circuits between the upper and lower windings of relay BGz and battery B2 and ground, re-
spectively. Thus, by so operating device K, cur-y rent will now now unidirectionally through the' "i" upper windings of relays BG1 and BGz over a circuit which includes rectiiier RKi, the upper wind.- ing of relay BG1, condenser C1, the generator MG, condenser C3, the upper winding of relay BGz, rectifier RKa, battery B2 and ground, Current will also ow unidirectionally through the lower winding of relays BG1 and BGz over a circuit which includes battery B1, rectifier RKz, the lower winding of relay BG1, condenser C2, generator MG, condenser C4, the lower winding of relay BGz, rectier RK4 and ground, The unidirectional currents now traversing both windings of relays BG1 and BGz will be superimposed upon the direct currents previously supplied to these windings by batteries B1 and B2. Thus an inf. creased current will traverse the windings lof relays BG1 and BGz and these relays will be held operated while the hand generator MG is operated. These relays remaining operated they will hold the Ytrunks TK1 and TK2 connected to the subscribers sets such as SS1 and SSz and not interfere with communication over the two trunk circuits.
The condensers C1 and C2 provide a low irnpedance path between generator MG and trunk TK1 for the alternating current generated .and condensers Cs and C6 provide a low impedance path between trunk TK1 and relay R0 Vso that only the generated current may actuate relay Ro. The return path for the generated current includes condensers Cv and Cs, trunk TK2 and condensers C3 and C4. The rectifying elements RK1 to RK4 prevent the ow of alternating current through the windings of the relay apparatus common to trunk TK1 or trunk TKz except in rectified form. Thus alternating current will be transmitted over the trunks acting as transmission paths extending between the two oflices, but the trunk control apparatus will receive only direct current.
The rect'iers RK1 to R-K4 interposed in the circuits between the hand generator MG and the windings of relays BG1 and BGz provide in effect a full wave rectifying circuit, Both halves of each cycle of alternating current produced by the generator MG will be rectified and the recti fied current will be added to the battery currents previously flowing through these relay windings, Thus the rectied currents and the battery currents will be caused rto aid each other,
increase the holding action of relays BG1 and BGz and prevent their chattering This is an important feature of this invention.
Fig. 2 shows schematically an arrangement for inserting the rectifiers RK1 to RKi of Fig. l into their respective circuits upon the operation of the hand generator MG. The crank of the hand generator MG when rotated controls a cam 2S, which in turn may move the insulating bar 33 to the left so asto open all of the contacts 3|, 32, 33 and 34 simultaneously. Contacts 3l and 32 bridge the rectiers RK1 and RK2, respectively, and contacts 33 and 34 bridge rectiers RKS and RK4, respectively. When the arm 3l) is caused to move to the left in response to the rotation of the crank of the generator MG, the contacts 3l to 34 will be opened, thereby inserting the rectiiers RK1 to RK4 in their respective paths, as already described hereinabove with respect to Fig, l. At the same time contact 35 will be closed to establish a path between the hand generator MG and the condensers C1 and C2. The contact 35, therefore, interposes the hand generator MG in series between the parallel condensers C1 and Cz andthe parallel condensers C3 and C4. These condensers `are connected to the trunk circuits as shown in Fig'l. The switching arrangement of Fig. 2 is automatic in operation and opens the bridge circuit to the rectiers just as soon as the crank of generator MG is properly rotated. Although the arrangement of Fig. 2 illustrates how the magneto generator MG may simultaneously close a plurality of contacts such as 3l to 35, it will be understood that the cam device 29 may close but one contact which in turn may control the operation of a relay (not shown), the relay controlling the contacts 3l to 35 which shunt the rectiers RK1 to RK4. The relay obviously may be located either at the station of the magneto telephone set MS or at the community dial oice CDO, The contacts l2-l4 associated with the relay may be adjacent to the relay or remote therefrom, as desired.
Although it has been stated that the magneto set may be operated whenever a busy condition develops on the trunk circuits between the two cilices, the magneto set may also be used even when the trunk apparatus is idle. The magneto phantom circuit provides an additional path between the two oices for special use both for signaling and talking during emergencies. The cost of the equipment required to set up the phantom circuit is quite small. The additional equipment is simple and may be appended to the trunk apparatus whenever` desired. The magneto phantom circuit will be operable whether or not the trunk circuits are transposed with respect to each other.
Although this invention has been disclosed in certain specic arrangements which are deemed desirable, it will be obvious that the general principles herein set forth may be embodied in many other organizations, widely diierent from those illustrated, without departing from the spirit of the invention as defined in the appended claims.
What is claimed is:
l. In a telephone system, the combination of a manual omce and a community dial -orcecon- -nected to each other by a pair of trunks, two
relays each connected to one of said trunks for controlling the connection of the trunk to subscribers circuits, a magneto telephone set including a magneto generator connected to said trunks as a phantom circuit, and means for preventing the magneto generator from falsely operating the said relays.
2. In a telephone system, the combination of two trunks, two repeating coils one terminating each trunk, two relays each connected to the midpoint of one of the repeating coils, a magneto telephone set including a magneto generator connected between the midpoints of said repeating coils so that said trunks may provide a phantom circuit for said magneto set, a plurality of rectifying elements, and means responsive to the operation of the magneto generator for inserting said rectifying elements in series with the windings of said relays so that only undirectional current may flow through the windings of said relays.
3. In a telephone system, the combination of a telephone line, a relay connected to said line, a magneto generator, means for connecting said magneto generator to said line to energize the winding of said relay, a rectifying element, and means responsive to the operation of said magneto generator to connect said reotifying element in series with the winding of said relay so that only unidirectional current may ilow through said relay windings.
4. In a telephone system, the combination of a relay having two windings, two rectifying elements, a telephone line connected to the windings of said relays, a magneto generator, and means responsive to the operation of said generator for connecting said rectifying elements to the windings of said relay so that only unidirectional current may flow therethrough.
5. In a telephone system, the combination of two trunks, two repeating coils each terminating one of said trunks, two relays one associated with each trunk and connected to the midpoint of the repeating coil of the associated trunk, a magneto telephone set including a magneto generator connected between the midpoints of the repeating coils of both trunks so that said trunks may form the side circuits of a phantom circuit, a plurality of rectifying elements, and means responsive to the operation of said magneto generator for inserting said rectifying elements in circuit with said relay windings so that only unidirectional currents may traverse the windings of said relays.
6. In a telephone system, the combination of two trunks, two repeating coils each terminating one of vsaid trunks, switching apparatus for said trunks, said switching apparatus including a relay for each trunk connected to the midpoint of the repeating coil associated with said trunk, a magneto telephone set including a magneto generator connected between the midpoints of the repeating coils associated with both trunks so that said trunks may provide a phantomcircuit for said magneto set, means responsive to the operation of the generator of said magneto set for transmitting only rectified current through the windings of said relays, and apparatus controlled by the current produced by said magneto generator.
'7. In a telephone system, the combination of a pair of trunks interconnecting two oiiices, a magneto telephone set including a magneto generator connected between both trunks at one of the ofces so as to provide a phantom circuit,
vsignal responsive means connected between both trunks at the other of the ofces to complete the phantom circuit, switching apparatus connected to each trunk, and means to prevent the operation of said switching apparatus by said magneto set.
8. In a telephone system, the combination of a pair of trunks interconnecting two offices, a telephone set including a ringing generator connected between both trunks at one of the oilces, signaling apparatus connected between both trunks at the other of the oices, said telephone set and said signaling apparatus providing with said trunks a phantom circuit,` switching apparatus connected to each trunk, and means to prevent the ringing generator of the telephone set 'from falsely operating said switching apparatus.-
9. In a telephone system, the combination of a pair of trunks interconnecting two oiices, a telephone set including a ringing generator connected between both trunks at one cf the oiices, signaling apparatus connected between both trunks at the other of the oflices, said telephone set and said signaling apparatus providing with said trunks a phantom circuit, switching apparatus connected to each trunk, and means responsive to the operation of the ringing generator of said telephone set to prevent the release of the switching apparatus by the current of said ringing generator when said switching apparatus is operated.
10. In a telephone system, the combination of two telephone oflices connected to each other by a pair of trunks, a plurality of subscribers circuits, two relays each connected to one of said trunks for controlling the connection of l the associated trunk to one of the subscriber circuits, a magneto telephone set including a magneto generator which may be connected to said trunks as a phantom circuit when said trunks are busy, and means to prevent saidmagneto generator from falsely operating said relays.
CHARLES STANLEY RHOADS.