US2435302A - Telephone system having a calling and supervisory signaling device - Google Patents

Description

Feb. 3, 1948. D. H. YOUNG ETAL. ,3

TELEPHONE SYSTEM HAVING A CALLING AND SUPERVISORY SIGNALING DEVICE Filed April 5, 1946 INVENTOR. DON/7. You/vs WATTfiRA/EYJ Patented Feb. 3, 1948 TELEPHONE SYSTEM HAVING A CALLING AND SUPERVISORY SIGNALING DEVICE Don H. Young, Valley Stream, and Frank R. Mallalieu, Forest Hills, N. Y., assignors to Dictograph Products Company, Inc., New York, N. Y., a corporationof Delaware Application April 3, 1946, Serial No. 659,230

8 Claims. (Cl. 17975) This invention relates to improvements in telephone systems, and it relates particularly to improvements in local batter telephone systems and switchboard circuits of the type disclosed in the Don H. Young application Serial No. 534,202, filed May 5, 1944, now Patent No, 2,393,354, dated J anuary22, 1946.

An object of the invention is to provide simplified local battery telephone systems having combined calling and supervisory signalling means.

Another object of the invention is to provide local battery telephone system in which a single signalling means serves 'both as :a call signal and a supervisory signal.

A further object of the invention is to provide telephone systems including signal-ling means of the electronic tube type that are responsive to call signals properly transmitted along the telephone lines and not responsive to-stray radio frequency signals picked up by the lines or inter pair line leakages.

Other objects of the invention will become .apparent from the following description of typical forms of telephone systems embodying the present invention.

In accordance with the present invention, we have provided a local battery telephone system in which an electronic glow tube is used, at the switchboard, for Signalling a call from a party, the tube being arranged also to indicate the end of the telephone call.

More particularly, theswitchboards of the type embodying the present invention ar provided with a plurality of electronic glow tubes, prefer- :ably having four elements including the cathode, two grids and a plate. One tube is provided for each station and is directl responsive to calls from that station.

The switchboard is provided with suit-able switching mechanism by means of which the operators telephone set can be connected with the line of the party making the call and the line of the called party and transmit a suitable signal to the'called party.

Each signalling tube is normall in a condition to be set into operation by a signal from the party making the call, except when the operator at the switchboard cuts in to answer the call or to-supervise the call.

The telephone sets in the party station are arranged to provide a signal for energizing the signalling tubes at the beginning and at the end of the -call so that the tube is energized and caused to glow at the beginning and at the end -'of the call, thereby keeping the operator advised as to the useof the telephone lines.

Such systems may be provided with suitable filter circuits whereby the undesired energization of the signal tubes by radio frequency signals picked up by the lines, and interpair leakage of the lines can becavoided.

For a better understanding of the present invention reference may be had to the accompanying drawings in which:

Figure 1 is a schematic wiring diagram of a typical system embodying the present invention; and

Figures 2, 3, 4 .and'5 are schematic diagrams of suitable filter circuits to he used in the telephone systemv shown in Figure 1.

Telephone systems of the type embodying the present invention and illustrated in Figure 1 of the drawings are useful for communications operations in the Armed Forces and in rural localities, inasmuch as they will operate satisfactorily under conditions that would completely disrupt service with the more sensitive and modern common battery systems. Thus, for example, when the lines are temporarily short-circuited between stations, the signalling tubes will not be caused to glow and even when there are substantial variations in the resistance of the wires or lines, effective signalling and message transmission is still possible.

The form of the invention disclosed in Figure 1 is a modification of the system disclosed in the Young application Serial No. 534,202 and the telephones provided in th party stations may be identical with those disclosed in that application. For example, the local telephone circuit for a party A may include a transmitter Ill and a receiver H which may be mounted in the usual wall, desk, or hand set type of casing. A switch I2 i interposed between the .line l3 and the receiver H which is responsive to removal of the receiver or the handset from the hook or cradle. The opposite side of the receiver II is connected .by means of a conductor M and the secondary winding I5 of a transformer IG-to the line l1. The transmitter H1 is connected .by means of the conductor l4 and another hook switch l8 to one pole of a battery l9, through the other pole of the battery l9 to the primary winding 20 of the transformer 15 and to the other side of the transmitter l 0,thereby constituting a talking circuit when the hook switch I8 is closed. One pole of the battery 19 is also connected by means of a conductor to the primary winding 2| of a step-up transformer 22. The opposite end of the Winding 2| is connected to one contact of a pulsating switch 23 which is connected to the opposite pole of the battery H. .An audible signalling member 24 is also connected between the The pulsating switchis so arranged that when the receiver is lifted from the cradle or hook, the contacts are set into vibration in order to produce a pulsating current that can be stepped up in open, with the result that the tube 3d is extinthe transformer 22 and transmitted to the central board in order to indicate at theswitchboard an incoming call. Likewise, whenth'e receiver or hand set is returned to the hook or cradle, the

pulsating switch 23 is set into operation to transmit a signal to the main switch board to indicate the end of the conversation or call.

The lines l3 and I1 terminate at the switch board in the contacts 26a and 26b respectively of r the plug 23. This plug normally is adaptedto be received in a jack 21 having the contacts 21a and 21b for engaging the plug contacts 26a and 26b respectively. The jack contacts 27a and Z'Ib are connected through the limiting resistors '28 and 29 to the grids 30a and 3% respectively of a fourelement glow tube 38. The glow tube 30 is provided witha plate 390 and a cathode 33312, the

latter being connected to the conductor 3! which 1 is in turn connected to one pole of a local bat-.

tery or other source of power 32.

The p ate 300 is connected by means of a conductor 33 to a switch contact 34a which normally engages a fixed contact 340 that is connected to the cor ductor 35 which is connected to the opposite pole of the local battery 32. The electronic tube circuit described above is such that normally. a potential is applied to the plate 360 and the cathode 30d, this potential. however, being insufilcient to cause a discharge between the plate sired, a relay 36 may be connected in the circuit between the battery 32 and the glow tube 36, so that an audible signal may be produced by the discharge or flow of current through the tube. The relay 36 may be connected, as illustrated, in the conductor 35.

In order for the operator at the switchboard to talk to the party, a switch is provided whereby the operators bus wires 31 and 38 may be conv nected to the lines l3 and I1. As shown, the bus wire 31 is connected to a fixed-contact 39a of a switch 39 and to a fixed contact 34d of the switch 34. The contact 39a cooperates with a normally open switch contact 39b which is connected to the line H. The contact 34d cooperates with a normally open contact 34c also connected to the line H. V

The operators talking circuit also includes a conductor #30 which connects the bus wire 38 to a fixed contact 41a of a switch 4! and to the fixed contact 42a of the switch 42. The fixed contact lla cooperates with a normally open contact Nb of the switch M, which is connected to one contact 43a of a jack c3 and to the movable contact 42b of the switch 42.

The contact 43b of thejack 43 is connected to the line H.

The fixed contact Me of the switch 4| is connected to the line I3.

The movable contacts 34:; and 346 and 42b party calling.

. 4 7 move simultaneously when the operators switch is moved in the direction indicated by the arrow identified as Talk," thereby disengaging the contacts 36a and Me and engaging the contacts 34d and 346 and also engaging the contacts 42aand 42b. With the contacts in this latter position, the

circuit between the battery 32 and the tube 30 is guished. At the same time, the operators bus wire 3? is connected through the contacts 346 and 3.4dto the line l1 and the bus 38 is connected 7 through thecontactslZa, 42b, Mb and M0 to the line l3so that the operator can converse with the The switchboard described above is provided withas'manytelephone circuits like that described above as there are parties in the system. A second signal system'corresponding to another party 3 is illustrative of a plurality of such additional stations. The system corresponding to the party B is provided with a plug 55, a jack 45 for receiving it, a glow tube signalling mecha nism ii, and the ringing and talking switches and 59 and a jack 5!! similar to the jack 43. When the party A Of the first described system desires to talk with the party B, the operator will withdraw the plug i5 from the jack 46 and insert it in the jack 43 of the A system. This connects the lines 5| and 52 of the system B with the lines I3 and i! respectively so that a conversation can be carried on between the party at station A and the party at station B.

In order to call the attention of the 'party at station B to the call, the operator at theswitchboard will actuate the control switch in the di rection of the arrow marked fRing" thereby disengaging the contacts Mb and H0 and'engaging the contacts Ala and Mb and at the same time engaging the contacts 39a and 39b. This operation disconnects the party A from the op-'- the jack contact 43b. When the ringing signal has been given, the operators switch may be restored to neutral position and the conversation may be carried on by the party A and the partyB through the connections described above.

At this time, the glow tube 30 will also be reconditioned for further energization, inasmuch as the potential from the battery 32 is again applied to the cathode 30c and the cathode 313d.

The operator may cut in at any time to determine whether the lines are still in service by merely moving the switch to the Talk position. At the conclusion of the conversation, when the party at station A restores his receiver or hand set to the hook or cradle, a, signal voltage of sufficient magnitude is transmitted from the vibratory switch 23 to the glow tube 30 to energize the grids 30a and 39b and cause the tube 30 to glow. The signal provided by the tube 30 advises the operator that the conversation is concluded and the operator may then withdraw the plug 45 from the jack 43 and reinsertitiqthe jack is to restore the switchboardto a condition whereby it may be used by the party "3 for calling other parties connected to the system.

Systems of the type described above are somewhat sensitive to radio frequency signals picked up by the telephone lines, particularly when the lines pass near a powerful radio transmitter. Also, false operation of the signalling tubes 30 or 41 may occur because of leakage between the pairs of telephone lines.

This can be overcome to a certain extent by means of the limiting resistors 28 and 29 in each of the circuits. These resistors may have a value in the range of 25,000 to 2 megohms and act to limit the current to the rated current of the particular tube used. This circuit gives some false signals in practice.

As shown in Figure '2, the false signals caused ing resistors 58 and 59 which are connected to the grids of the tube as shown in Figure 3. In-

asmuch as the grids of the tube normally present a very high impedance to the line, spurious voltages frequently may be reduced so that they will not be troublesome merely by providing a loading resistor 51 having a value between 5,000 and 50,000 ohms across the input.

A somewhat different arrangement is disclosed in Figure 4 which, in addition to loading the line, tends to balance it to the tube to ground and maintains the tube grids at switchboard ground potentials. In this form, two resistors 60 and 6! are connected across the line and the midpoint is connected to the battery 32 through a third resistor 62. The sum of the values of the resistances 60 and El preferably should be somewhat less than that of the limiting resistors 63a and 631). If desired, the resistors 69 and 6! may be connected across the grids instead of across the lines- The form disclosed in Figure 5- is the preferred form, inasmuch as it stabilizes the system against both interpair leakage and radio frequency voltages. In this form, a pair of resistances 6'4 and 55 are connected across the line and a pair of condensers 66 and 6'! ar connected across the grids of the tube 38". The midpoint between the resistances E4 and 65 and the condensers $6 and 51 are connected to ground or to the battery 32" with a, resistor 68 connected between the midpoints referred to above. By the use of this latter circuit, radio frequency signals are filtered out and the resistance of the circuit is such that interpair leakage potentials have no eifect upon the energization' of the tube.

From the preceding description, it will be apparent that we have provided a simplified form of local battery telephone system in which fewer tubes are required for providing call and supervisory signals and in which the system is rendered insensitive to radio frequency voltages induced in the lines and leakage between the pairs of lines. r

It will be understood that there may be some variations in the arrangement of the operators 6 switching mechanism-andthat other means thanvibrating' switches may be used for igniting" the glow tube. Therefore, the form of the invention described above should be considered as illustrative and not as'limiting the scope of the following claims.

We claim:-

1. In a local battery telephone system, the combination of at least two, two wire telephone lines,v telephone sets connected to said lines, a switchboard, a glow tube at the switchboard corresponding to each of said telephone lines, each tube having a cathode, a plate and a pair of grids,- a switchboard operators telephone-set at said switchboard,.means connecting the wires of each telephone line to different grids of its corresponding glow tube; means for applying a potential to said cathode and plate or each tube insufficient to; cause said tubes to glow but sufficient. tomaintain said tubes glowing upon energizatlon of said grids, means at the telephone set co'nnected'to each line for applying. a potential to said lines sufficient' to energize said grids of the corresponding tube and cause said tube to glow, and a switching means for connectingsaid Opel at'ors telephone set t'o a' telephone line andsimultaneou'sly removing the potential from the plate and cathode of thetub'e corresponding to the line to which the operators set is connected.

2. In a local battery telephone system, the combination of at least two, two-wire telephone lines, a telephone connected to each of said lines, a switchboard, electronic glow tubes at the switchboard corresponding to each telephone line, each tube having a plate, a cathode and two grids, jacks having a pair of contacts each connected to different grids of a tube, a plug fitting said jack having separate contacts connected to the wiresof a line and receivable in the jack of the corresponding tube to connect said lines to the grids of its corresponding tube, means for applying apotential to the plates and cathodes of said tubes of a magnitude insufiicient to cause said tubes to glow but sufficient to maintain said tubes glowing after energization of said grids, means at each of said telephone sets for energizing the grids of its corresponding tube to cause said corresponding tube to glow, other jacks corresponding'to each line at said switchboard, normally engaged switching means connecting each jack to its corresponding telephone line, each of said other jacks being adapted to receive the plug of the line not corresponding to the other jack to interconnect said lines, said switching means being operable to disconnect said other jack from its corresponding line. v

3. In a local battery telephone system, the com- .bination of at least two, two-wire telephone lines, a telephone connected to each of said lines a switchboard, electronic, glow tubesat the switchboard corresponding to each telephone line, each tubehaving a platey'a cathode and two grids, jacks; having a pair of contacts each connected to difierent grids of a tube, a plug fitting said jack having separate contacts connected to the wires of a line and. receivablein the jack of the corresponding] tube to connect said lines to the .grids of itscorresponding tube, means for applying a potential to the plates and cathodes of said tubes of;a magnitude ins'uiiicient to cause said tubes toglow but sufiicient to maintain said tubes glowing. after energization of said grids, means at each of said telephone sets for energizing the grids of its corresponding tube to cause saidcorresponding tube to' glow, other jacks-cor'-- to said other jack when the latter is disconnected from it corresponding line.

4. In a local battery telephone system, the combination of at least two, two wire telephone lines, telephone sets connected to said lines, a switch board, a glow tube at the switchboard corresponding to each of said telephone lines, each tube having a cathode, a plate and a pair of grids, a switchboard operators telephone set at said switchboard, means connecting the wire of each telephone line to difierentgrids of its corresponding glow tube, means for applying a potential to said cathode and plate of each tube insuificient to cause said tubes to glow butsufiicient to maintain said tubes glowingupon energization of said grids, means-at each telephone set connected to a telephone line for applying a potential to said line suficient to energize the grids of the corresponding tube and cause said tube to glow, means interposed between each :line and its corresponding tube for filtering out potentials due to interpair line leakages.

5. In a local battery telephone system, the combination of at least two, two wire telephone lines, telephone sets connected to said lines, a switchboard, a glow tube at the-switchboard corresponding to each of said telephone lines, each tube having a cathode, a plate and a pair of grids, a switchboard operator's telephone set at said switchboard, means connecting the wires of each telephone line to different grids of its corresponding glow tube, means for applying a potential to said cathode and plate of each tube insuflicient to cause said tubes to glow but suflicient to maintain said tubes glowingupon energization of said grids, means at each telephone set connected to a telephone line for applying a potential to said line sufiicient to energize the grids of the corresponding tube and cause said tube to glow, means interposed between each line and its corresponding tube for filtering out po- ,tentials due to pickup of radio frequency signals -by said lines. 6. In a local battery telephone system, the combination of at least two, two wire telephone lines, telephone sets connected to said lines, a switchboard, a glow tube at the switchboard cor:- responding to each of said telephone lines, each tube having a cathode, a plate and a pair of grids, a switchboard operators telephone set at said .rswitchboard, means connecting the wires of each :telephone line to different grids of its corresponding glow tube, meansfor applying a po'- ;tential to said cathode and plate of each tube insufficient to cause said tubes to glow but sumcient to maintain said tubes glowing-upon energization of said grids, means at each telephone set connected to a telephone line for applyinga potential to said line sufficient to energize the grids of the corresponding tube and cause said tube to glow, means interposed between each line and its corresponding tube for filtering out potentials due to interpair line leakages and pick- .up of radio frequency signals by said lines.

7, In a local battery telephonezsystem, the combination-of at least two telephone lines, a

8 o V 7 party telephone set connected to said each of said lines, a switchboard, an electronic glow tube corresponding to each telephone line at saidswitchboard, each tube having a plate, a' cathode and a pair of grids, means connecting each telephone line to the grids of its corresponding tube, means at the switchboard for, applying a potential is the plate and cathode of each tube, said potential be.-

' .ing insufiicient to cause said tubes to glow, but

sufiicient to maintain said tubes glowing upon energization of the grids thereof, means operable at each telephone'set for energizing the grids of its corresponding tube sufficiently to cause'said tube to glow, an operators telephone set atisaid switchboard, means at said switchboard for supplying a ringing potential to a party telephone set, switching means at said switchboardcorre-r partytelephone set connected to said each of said lines, a switchboard, an electronic glow tube cor-' responding to each telephone line at said switchboard, each tube having a plate, a cathode and a pair of grids, means connecting each telephone line to the grids of its corresponding tube, means at the switchboard for applying a potential to the plate and cathode of each tube, said 'poten tial being insufficient to cause said tubes to glow,

but sufiicient to maintain said tubesglowing upon energization of the grids thereof, means operable at each telephone set for energizing the grids of its corresponding tube sufficiently to cause said tube to glow, an operators telephone set at said switchboard, means at said switchboard for sup plying a ringing potential to a party telephone set, switching means at said switchboard correfsponding to each party telephone set'for connect ing said operators set to the corresponding party set and simultaneously removing the potential from the plate and cathode of said corresponding tube, means at said switchboard for connecting a telephone line corresponding to a called party to another telephone line corresponding to a calling party, and simultaneously disconnecting the grids of the tube corresponding to the called party set from its corresponding telephone" line; said switching means further being operable to dis connect said lines and connect saidsource jo'i ringing potential to the telephone line corre sponding to the, called party. DON H. YOUNG. v

'F'RANK' R. MALLALIEU,

REFERENCES CITED The following references are of record in the file of this patentz" UNITED STATES PATENTS

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