US2408299A

US2408299A - Selective signaling system

Info

Publication number: US2408299A
Application number: US564127A
Authority: US
Inventors: Davis Rowland Fenner
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1944-11-18
Filing date: 1944-11-18
Publication date: 1946-09-24
Anticipated expiration: 1963-09-24

Description

Sept. 24, 1946. DAVIS 2,408,299

' I SELECTIVE SIGNALING SYSTEM Filed NOV. 18, 1944 Statwn ,5 Station 6 Paul .Bridg Ring Statwn 2 Mart mll'p Station 4 -.Hv't 1/mTip INVENTOI Z BY t ' ATTORNEY Patented Sept. 24, 1946 UNITED STATES PATENT OFFICE- v SELECTIVE SIGNALING SYSTEMT Rowland'Fenner Davis, Tuckahoe, N..Y., assignor to American Telephone and Telegraph Com-- pany, a corporation. of New York. Application November. 18, 1944, Serial No. 564,127

This invention relatesto selective systems and more particularly to arrangements for causing the selective operation of electro-responsive devices such, for example, as telephone ringers on.

a multi party telephone line.

One of the systems utilized in the past to accomplish selective signaling on multi-party telephone lines has utilized two stations connected between the ti side of the line and ground and two stations connectedbetween the ring side of the line and ground. The stations connected to the tip side of the line would be oppositely poled and one would operate when negative pulsating current was applied to the tip and the other would operate when positive pulsating current was ap-' plied to the tip. In like manner the two stations connected to the ring side of the line would be oppositely poled and one would" operate when negative pulsating current was applied to the ring and the other would operate when positive pulsat ing current was appliedto the ring; Such a system provides means for selectively signaling'four stations. The arrangements of th'ein'ventionprovidemeans whereby additional stations may be added to such asystemandthese additional stations may alsobe selectively signaled without-interference to or from the'previously mentioned stations. In one embodiment of the invention this is accomplished by. bridging oppositely poled stations across the linezand providing means at the central ofiice for preventing: the signaling currents normally used for operating theoriginal four stations from affecting th'ebridged: stations. Also the bridged stations are so connectedthat the signaling currents 1 applied to selectively perate them willnot affect the original four stations. Other. objects and featuresof theinven- 'tion will appear more fully. from the detailed description thereof hereinafter given.

The invention may be more fully understood from the following description, together withthe accompanying drawing, in the figure of which is shown a circuit;- diagramillustrating a; preferred The connections of'these tubes are such-that-thestations land 2-are oppositely poled. connected between the ring side of the line and ground would be the signal responsive arrangements of

stations

3 and 4. These each include the ringers such as 12 and I4 connected to the ring side of the line through the gas-filled tubes II and I3.

I 4 Claims. (Cl. 179-46) 7 The connections ofthe; gas-filled tubesare such that the ringers are oppositely poled. Bridged across the line are shown the signal responsive means of

stations

5 and 6. Each of these includes a ringer such as the ringers I6 and 18. These ringers are bridged across the line by means of the gas-filled tubes l5 and I! in such a manner that; they are oppositely poled. At the central ofli ce would be provided a plurality of switches such as S1, S2, S3, S4, S5 and S6 for selectively signaling the

respectivestations

1,2, 3, 4, 5 and 6.

V Y switch S1 would be operated. This would apply negative pulsating current to the tip side of the line; This negative pulsating-current, in a manner well-known in the art, would cause-the gas-filledtube I to break down and operate the ringer 8. Thenegative To signal station I I,

pulsating current applied to the tip side of the be the frequency of line, however, would not operate the ringer H], as the arrangements at station 2 are oppositely poled with respect to those of station I. 'In arrangements used. in the past, the operation of the switch S1 would apply ground to the ring side of the, line duringv the ringing period to avoid excessive noise on other cable pairs due to cross induction. However, in accordance with the arrangements' o-fthis invention the switch S1 will connect to thering side of the lineone or more anti resonant circuits such as l9 and 20. The

anti-resonant circuit 25 would present a high impedance'at, for example; 20 cycles, which mightthe pulsating current applied to the tip side of the line. The introduction of this impedance by the anti-resonant circuit 20 would prevent the operation of the tubes and ringers at stations 5. and 6. Because of the unsymmetrical wave shape of the pulsating current appliedto the tip of the. line, it might be desirable to provide an additional; anti-resonant circuit such as l9 to introduce sufficient impedance to,

the second harmonic of. the pulsating current which might be transmitted over the line, so that this second harmonic would not operate the gasfilled tubes l5 and If! of

stations

5 and 6. It is pointed out that as the circuits is and 20 are not anti-resonant at'the higher noise frequencies they efiectively. ground the ring side of the line with respect to these frequencies and hence prevent exces's'ivei noise on other cable pairs due to cross induction. To operate the signal responsive means at station 2 the switch. S2 would be operated. This .would apply positive-pulsating current to the tip side. of'the line and, in a manner well-known inthe art, would cause the gas-filled tube, 9 to operate and cause the ringer i0 too-perate,butit.would1have no, effect. on the gas-filled tube l and ringer 8'. In.like manner, the operation of the switch Sewould connect the antipulsating current or harmonics thereof would not operate the signal responsive apparatus at stations 5 and B. In a similar manner the operation of either the switch S3 or S4 would cause the signal responsiveapparatus at station 3 or station 4 to operate by applying either negative pulsating current or positive pulsating current to the ring side of the line. When switch S3 is operated, the

anti-resonant circuits

23 and 24 would be connected to the tip side of the line, and when switch S4 is operated the anti-resonant circuits 25 and 26 would be connected to thetip side of the line to prevent the operation of the signal responsive apparatus at stations 5 and. 6. To operate the signal responsive apparatus at station 5, the switch S5 would be operated. This would apply negative pulsating current out over the tip side of the line and back over the ring side of the line, and would cause the gasfilled tube I5 to break down and operate the ringer IS. The gas-filled tubes utilized have a definite break-down voltage as, for example, of between 65 and 70 volts. The voltage connected to both sides of the line by the operation of switch S5 is sufiicient to operate the gas-filled tube 15. However, this Voltage will not operate the

tubes

1 and 13 because they would be connected in series with each other and the resulting voltage applied thereto would be too low. In like manner, the voltage applied-to both sides of the line would not operate the gas-filled tubes 9 and l I, as they would be connected in series with each other and I the resultant voltage would be too low to cause them to operate. In like manner, the operation of switch S6 would apply a positive pulsating current to both sides of the line of sufiicient voltage to cause the tube I! to break down'and operate the ringer 18 at station 6. As this voltage would be applied to tubes 1 and I 3 in series and to tubes 5 and I I in series, the resultant voltage would not be sufficient to break these tubes down.

While this invention has been disclosed as embodied in certain specific forms which are deemed desirable, it is understood that it is capable of embodiment in many and other widely varied form-s without departing from the spirit of the invention as defined by the appended claims.

What is claimed is:

1. A line having a plurality of signal responsive devices connected thereto, certain of said devices being oppositely poled with respect to each other and operatively connected between one side of said line and ground, certain of said devices being oppositely poled with respect to each other and operatively connected between the other side of said line and ground, certain of said devices being oppositely poled with respect to each other and operatively bridged across said line, switching mechanism for connecting positive or negative pulsating current between one side of said line and ground to selectively operate any of the signal responsive devices connected to said side of the line and means connected by said switching mechanism between the other side of the line and ground for presenting sufficient impedance to said pulsating current to prevent its operation of said devices bridged across said line.

2. A line having a plurality of signal responsive devices connected thereto, certain of said devices being oppositely poled with respect to each other and operatively connected between one side of said line and ground, certain of said devices being oppositely poled with respect to each other and operatively connected between the other side of said, line and ground, certain of said devices being oppositely poled with respect to each other and operatively bridged across said line, switching mechanism for connecting positive or negative pulsating current between one side of said line and ground to selectively operate any of thesignal responsive devices connected to said side of the line, means connected by said switching mechanism between the other side' of the line and ground for presenting suflicient impedance to said pulsating current to prevent its operation of said devices bridged across said 'line, and additional switching means for connecting positive or negative pulsating current across said line to selectively operate any of said signal responsive devices bridged across said line.

3. A line having a plurality of signal responsive devices connected thereto, two of said devices being oppositely poled with respect to each other and connected between one side of said line and ground, another two of said devices being oppositely poled with respect to each other and connected between the other side of said line and ground, another two of said devices being oppositely poled with respect to each other and bridged across said line, switching mechanism for connecting positive or negative pulsating current between one side of said line and ground to selectively operate either. of the signal responsive devices connected to said side of the line, circuits anti-resonant at the frequency of the pulsating current and harmonics thereof, and means controlled by said switching means for connecting said anti-resonant circuits between the other side of the line and ground to prevent the pulsating current or harmonics thereof from operating said devices bridged across said line.

4. A line having a plurality of signal responsive devices connected thereto, tWo of said devices and operatively connected'between the other side of said line and ground, another two of said devices being oppositely poled with respect to each other and operatively bridged across said line, switching mechanism for connecting positive or negative pulsating current between one side of said line and ground to selectively operate either of the signal responsive devices connected to said side of the line, means connected by said switching mechanism between the other side of the line and ground for presenting suificient impedance to said pulsating current to prevent its operation of said devices bridged across said line, and additional switching means for connecting positive or negative pulsating current across said line to selectively operate either of said signal responsive devices bridged across said line, each of said signal responsive devices including a gas-filled discharge tube and a ringer connected to said linethrough its associated tube, the break-down voltage of each tube and the voltage of the pulsating current utilized being such that the application to a single tube of the voltage of the pulsating current will cause it to operate but the application of the voltage of the pulsating current to two of said tubes connected in series will not cause them to operate.

ROWLAND FENNER DAVIS.