[go: up one dir, main page]

US1891594A - Method for timing toll telephone circuits - Google Patents

Method for timing toll telephone circuits Download PDF

Info

Publication number
US1891594A
US1891594A US362693A US36269329A US1891594A US 1891594 A US1891594 A US 1891594A US 362693 A US362693 A US 362693A US 36269329 A US36269329 A US 36269329A US 1891594 A US1891594 A US 1891594A
Authority
US
United States
Prior art keywords
indicator
telephone
circuit
time
circuits
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US362693A
Inventor
Henry W Grimm
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to US362693A priority Critical patent/US1891594A/en
Application granted granted Critical
Publication of US1891594A publication Critical patent/US1891594A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M3/00Automatic or semi-automatic exchanges
    • H04M3/08Indicating faults in circuits or apparatus
    • H04M3/12Marking faulty circuits "busy"; Enabling equipment to disengage itself from faulty circuits ; Using redundant circuits; Response of a circuit, apparatus or system to an error

Definitions

  • timing toll telephone circuits and relates to certain systems, methods, and apparatus used to determine the intervals of time during which the telephone circuits are used, in
  • the chief purpose of this invention i s to pr ide systems, methods and apparatus to substantiallysimultaneously notify both the operator and the user of the telephone toll circuits of the beginning, end, divisions, and
  • Another purpose of the invention is to provide a warning signal for the benefit of the user a brief interval prior to theclosing of the tollperiod, to warn him that the time will soon expire.
  • Fig. 1 illustrates the system in one of its tosimplest and most basic'emhodiments.
  • Fig.2 is a similar view of a modified construction and arrangement thereof.
  • Fig. 3 shows a stilldifferent arrangement thereof. 7 p V F
  • the reference numbers 1 and 2 indicate two subscribers stations wired in system in the usual manner, said stations being shown at one side of a broken line 3, while on the other side of said line is indicated a central office equipment includinga battery l which provides the usual talking current for the system,'thru a retardation coil 5. All of the apparatus of the system is of the usual type, and only sufficient portions thereof are shown in the drawings, to properly illustrate the invention.
  • a shaft A is continuously rotated at predetermined speed in the direction indicated by the arrow, by a suitable time measuring device, not shown in the drawings.
  • a point indicator B is attached to the shaft A by suitable friction or other means which causes said indicator to-rotate with and at the same speed as the shaft at such times as the "movement is not interfered with.
  • Said indicator is held normally, however, in a given position by means of a pin H inserted in the path of the indicator, and acting as a stop therefor. Other means can be substituted for that shown, or the indicator can be held manually from operation. Upon being released the indicator makes a complete revolution with the shaft A during of time.
  • the stop H which is of a suitable type to be manually released or reset, holds the indicator stationary at a position on the dial C, near, and counter-clockwiseflto the marking D; V I
  • a bell-crank lever formed of a short arm I and long flexible arm I with a pivotal point at P.
  • the arm I' is in the line of rotation of the indicator B, which moves the arm momentarily upwards in its movement beneath the same.
  • This also elevates the arm a predetermined period 85 p electrically connected with the telephone cir- Y cator B has made one full cuit, as indicated at M and N.
  • the relative positions of the bell and transmitter are such that the audible vibrations from the bell effectively reach the transmitter and cause the same to function, thus varying the current in the telephone circuit, which variations substantially simultaneously produce corresponding audible vibrations in the receivers of the telephone circuit.
  • Substantially simultaneously with'the first and second signals for the operator, respectively corresponding audible signals for the users of the telephone circuit are produced in the receivers at stations 1 and 2, caused by the audible vibrations of the first and second signals for the operator, respectively from K, reaching and causing the transmitter L, electrically connected with the telephone circuit, to function and thus vary the current in the telephone circuit.
  • the indicator B continues to rotate, in a similar manner similar time intervals will be measured with each full-rotation, and a similar signal for the operator, together with a corresponding signal for the users, synchronized with each other, will in like manner be given at the end of each time interval measured, which will also serve as a signal for the beginning of the next time period.
  • an electrically operated means for signalling the operator is sul stituted for the mechanically operated signalling means shown in Fig. 1.
  • a terminal connection 0 is so placed on the dial C that the yielding flexible tip P of the indicator B in its rotation momentarily makes electrical contact with O at the position D, simultaneously closing a circuit extending from a battery Q, through a brush R, slip-ring S suitably mounted on the pointer B, indicator B, tip P, contact O, and lamp T to the battery Q, and circuit extendin from a battery U through a brush V, ring pointer B, tip P, and contact 0 through the telephone circuit to battery U.
  • the momentary closing of said circuits gives to the operator a visible signal by lighting the lamp T, and to the users a corresponding signal, substantially synchronized with the operators signal, by varying the current in the telephone circuit by the voltage momentarily impressed on it from the battery U.
  • a. telephone receiver V in the same circuit with the lamp T provides a means to signal the operator audibly.
  • An electrically operated bell X in the circuit extending from the battery U acts in conjunction with the transmitter L to vary the current in the telephone circuit in a similar manner to the mechanically operated bell in Fig. 1.
  • Terminal contacts Y and Y mounted in a similar manner to the contact 0 at positions near each other on the dial C countter clockwise to the marking D, are both electrically connected to both of the circuits extending from the batteries Q and U.
  • the indicator B after passing the point D in any full rotation momentarily closes both of said Y circuits simultaneously, first by making contact with Y and again by making contact with Y thus providing means for substan tially simultaneously giving a signal to both operator and users, which may be differentiated from that made when the indicator B makes a contact with terminal 0, and which may serve as a warning singal to the operator and users to get ready to carry out possible predetermined procedures at the end of the interval of time which will end with the signal given when the rotary movement of the indicator causes it to again make contact with terminal 0.
  • the indicator B may be associated and interconnected with a suitable registering device for registering the number of full and fractional revolutions it makes after the stop H is released. Said indicator and suchregistering device maybe associated and interconnected with a suitable recording device to record the registrations. Suitable means may be employed to instantly return the in dicator, the registering device, and the recording device to a starting position.
  • the indicator B, the registering device and the recording device may be associ ed anc interconnected with a suitable time indicating device, such as a clock, to show the relation of the time intervals to the time of day.
  • I may employ any suitable type of time interval measuring, indicating, registering and recording means, any suitable electrically or magnetically operated stop release in place of the manually operated release described for actuating the stop H, and other suitable means for varying the current in the telephone circuit to produce th audible signals in the receivers.
  • the means employed to vary the current in the telephone circuit is shown connected directly to such circuit at M and N, said means may be connected to said circuit by any other suitable means such as by induction, a link circuit.
  • any number of'terminal contacts similar to that shown at O and similarly placedo-n other positions on the dial 0, such as at E, F, and G, and similarly connected to the circuits, may be employed to give signals corresponding to predetermined divisions of the interval of time measured by a full revolution of the indicator B.
  • These contact terminals may vary' as to size of contact surfaces and may be grouped to give several types of signals which can be identified one from the other.
  • the terminal contacts may be so mounted as to be adjustable to difierent operable positions necessary to make contact with the indicator B by suitable means actuated by said indicator and the shaft A in their rotation, to give a different type of signal as the indicator passes a given position on the dial C in successive rotations.
  • Various numbers of telephone receivers may be in the telephone circuit, each providing the audible signals impressed upon the tele phone circuit.
  • Any other suitable current supply may be substituted for the battery U in Fig. 2, such as A. C. current of any frequency within the audible range, to produce signals in the receivers of desired pitch.
  • Any other suitable electrically actuated sound producing device may be substituted for the bell X shown in Fig. 3.
  • Combination wire and wireless telephone circuits may be used as well as the wire telephone circuits shown.
  • Operator controlled means may be associated and inter-connected with the indicator B to hold the same sta tionary for periods at any position on the central operators station; an element-nordial C after the indicator starts to rotate from the starting position D, thus increasing the interval of time taken by the indicator to make a full revolution when thus held, sub.- stantially by the length of time such indicator is held,.thus providing a means for subtracting from the time interval a telephone circuit is used, any periods of inoperable interference in the telephone circuit.
  • Means may be provided to give the users an identifiable audible signal in the receivers during the periods when the indicator is held.
  • the audible signals in the receivers may be of such a nature in respect to their duration, volume, and musical pitch as to cause and yet be distinct. 7
  • said member for movement by the latter, releasable-means for holding said element normally against movement during movement of said member,said means being adapted for release to enable said element to move with said member when a circuit is established between a pair of subscribers stations-in the telephone system and when conversation between said stations begins, and means operable by movement of said element to effect signal variations in the current of the subscribers line at predetermined intervals of time.
  • releasable means In combination with a telephone system including subscribers stations and lines; an element normally held against movement and movable at a predetermined rate of speed when released, releasable means holding said negligible interference withthe conversation element normally held against movement and movable at a predetermined rate of speed when released, releasable means holding said element normally against movement, said means being adapted for release when an operative circuit has been established between a pair of stations in the telephone system, a sound producing device, means under the control of said first named means operable immediately following release thereof to cause said device to produce sound and thereafter to repeat said sound following the elapse of predetermined periods of time, and a transmitter located adjacent to said sound producing device and connected with the subscribers line.
  • a telephone system including a subscribers line; a shaft rotatable constantly at a fixed rate of speed, an element having a slip connection with said shaft, a releasable stop to hold said element against rotation, said element being adapted to rotate with said shaft when'said stop is released, and means operable by said element immediately following its release to effect asignal variation in the current of said subscribers line and thereafter to repeat said signal variation following the elapse'of pre determined periods oftime.
  • indicating means operable by the central station operator to determine a period of use of an operative circuit between a pair of stations in the telephone system, and means under the control of said first named means to effect and repeat signal variations periodically in the current of said circuit, synchronized with the indications of said indicating means.

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Description

De c. 20, 1932. H. w. GRIMM METHOD FOR TIMING TOLL TELEPHONE CIRCUITS s She ets-Sheet 1 Filed May 15, 1929 M1 ml FIE l W gart/ mil;ZENTOR. wbm- Dec. 20, 1932. H. w. GRIMM METHOD FOR TIMING TOLL TELEPHONE CIRCUITS Filed May 13. 1929 5 Sheets-Sheet 2 FIE'E 9kg INVENTOR BY MXW MATMRNEY Dec.
H. w. GRIMM 1,891,594
METHOD FOR TIMING TOLL TELEPHONE CIRCUITS Filed May 13, 1929 3 Sheets-Sheet 3 M A TTORNEY Patented Dec. 20, 1932 HENRY W. GRIMM, OF MOLINE, ILLINOIS METHOD FOR TIMING TOLL TELEPHONE CIRCUITS Application filed May. 13, 1929. Serial No. 362,693.
for timing toll telephone circuits, and relates to certain systems, methods, and apparatus used to determine the intervals of time during which the telephone circuits are used, in
telephone exchange systems in which a toll or charge, computed on a basis of time periods or intervals, is made by the operators to the subscribers or users, for the'use of '10 interconnected telephone circuits, employing link circuits or otherwise. Under the present arrangement and manner of conducting the toll circuits there is no adequate means for appraising the user of the system of the 415 time when the charge period starts, when certain graduated divisions of such period terminate, and when the full period of time has closed, or is about to close. The present methods made use of by the toll operators are also crude and unreliable.
The chief purpose of this invention i s to pr ide systems, methods and apparatus to substantiallysimultaneously notify both the operator and the user of the telephone toll circuits of the beginning, end, divisions, and
multiples'of the predetermined periods of time, as they are being measured, determined, registered, and recorded for the purpose of computing the charges for. the use of the telephone circuits, and thus provide improved service as compared with the service possible in systems where only the operator obtains this information.
Another purpose of the invention is to provide a warning signal for the benefit of the user a brief interval prior to theclosing of the tollperiod, to warn him that the time will soon expire.
0 The above named and other features and advantages of the invention will more fully appear from the following specification, reference being had to the accompanying drawings, which are all of a diagrammatic character, andin which the same reference characters are employed to designate similar parts throughout.
In said drawings: Fig. 1 illustrates the system in one of its tosimplest and most basic'emhodiments. Y
The invention has reference to a method Fig.2 is a similar view of a modified construction and arrangement thereof.
Fig. 3 shows a stilldifferent arrangement thereof. 7 p V F Calling attention first to Fig. 1 of the drawings, the reference numbers 1 and 2 indicate two subscribers stations wired in system in the usual manner, said stations being shown at one side of a broken line 3, while on the other side of said line is indicated a central office equipment includinga battery l which provides the usual talking current for the system,'thru a retardation coil 5. All of the apparatus of the system is of the usual type, and only sufficient portions thereof are shown in the drawings, to properly illustrate the invention.
A shaft A is continuously rotated at predetermined speed in the direction indicated by the arrow, by a suitable time measuring device, not shown in the drawings. A point indicator B is attached to the shaft A by suitable friction or other means which causes said indicator to-rotate with and at the same speed as the shaft at such times as the "movement is not interfered with. Said indicator is held normally, however, in a given position by means of a pin H inserted in the path of the indicator, and acting as a stop therefor. Other means can be substituted for that shown, or the indicator can be held manually from operation. Upon being released the indicator makes a complete revolution with the shaft A during of time.
C indicates a stationary dial, around which the indicator B rotates, said dial being pro vided with graduated markings at D, E, F, and G. The stop H, which is of a suitable type to be manually released or reset, holds the indicator stationary at a position on the dial C, near, and counter-clockwiseflto the marking D; V I
Supported in proximity to the indicator B is a bell-crank lever formed of a short arm I and long flexible arm I with a pivotal point at P. The arm I'is in the line of rotation of the indicator B, which moves the arm momentarily upwards in its movement beneath the same. This also elevates the arm a predetermined period 85 p electrically connected with the telephone cir- Y cator B has made one full cuit, as indicated at M and N. The relative positions of the bell and transmitter are such that the audible vibrations from the bell effectively reach the transmitter and cause the same to function, thus varying the current in the telephone circuit, which variations substantially simultaneously produce corresponding audible vibrations in the receivers of the telephone circuit.
It is thought that the following descriptionof the operation of the system and apparatus shown in Fig. 1 will give a better understanding of the invention. When the operator releases the stop H, the indicator B starts to rotate with the shaft A, and with the speed of said shaft. Immediately after starting, the indicator momentarily lifts the hammer J by engaging with the trip lever I. The hammer J falls and strikes the bell K as the indicator B is at the point D in its rotation, causing the bell K to vibrate audibly. This audible signal notifies the operator of the beginning of a predetermined interval of time, which will end after the indirevolution, at which instant the operation which produced the first signal will have been repeated, causing a second signal which notifies the operator of the ending the interval of time. Substantially simultaneously with'the first and second signals for the operator, respectively corresponding audible signals for the users of the telephone circuit are produced in the receivers at stations 1 and 2, caused by the audible vibrations of the first and second signals for the operator, respectively from K, reaching and causing the transmitter L, electrically connected with the telephone circuit, to function and thus vary the current in the telephone circuit. As the indicator B continues to rotate, in a similar manner similar time intervals will be measured with each full-rotation, and a similar signal for the operator, together with a corresponding signal for the users, synchronized with each other, will in like manner be given at the end of each time interval measured, which will also serve as a signal for the beginning of the next time period.
As shown in Fig. 2, an electrically operated means for signalling the operator is sul stituted for the mechanically operated signalling means shown in Fig. 1. A terminal connection 0 is so placed on the dial C that the yielding flexible tip P of the indicator B in its rotation momentarily makes electrical contact with O at the position D, simultaneously closing a circuit extending from a battery Q, through a brush R, slip-ring S suitably mounted on the pointer B, indicator B, tip P, contact O, and lamp T to the battery Q, and circuit extendin from a battery U through a brush V, ring pointer B, tip P, and contact 0 through the telephone circuit to battery U. The momentary closing of said circuits gives to the operator a visible signal by lighting the lamp T, and to the users a corresponding signal, substantially synchronized with the operators signal, by varying the current in the telephone circuit by the voltage momentarily impressed on it from the battery U.
As shown in Fig. 3, a. telephone receiver V in the same circuit with the lamp T provides a means to signal the operator audibly. An electrically operated bell X in the circuit extending from the battery U acts in conjunction with the transmitter L to vary the current in the telephone circuit in a similar manner to the mechanically operated bell in Fig. 1. .Terminal contacts Y and Y mounted in a similar manner to the contact 0 at positions near each other on the dial C countter clockwise to the marking D, are both electrically connected to both of the circuits extending from the batteries Q and U. The indicator B after passing the point D in any full rotation momentarily closes both of said Y circuits simultaneously, first by making contact with Y and again by making contact with Y thus providing means for substan tially simultaneously giving a signal to both operator and users, which may be differentiated from that made when the indicator B makes a contact with terminal 0, and which may serve as a warning singal to the operator and users to get ready to carry out possible predetermined procedures at the end of the interval of time which will end with the signal given when the rotary movement of the indicator causes it to again make contact with terminal 0.
While I have purposely chosen to show this invention in its most simple and basic embodiments in order that it may be more easily and clearly understood, I do not desire to limit myself to them, but may employ any of the possible various modifications and elaborations in the details of construction and arrangements of circuits and parts which do not depart from the spirit of my invention and are restrictedonly by the scope of the following claims, many of which will be obvious to those skilled in the art, and several of which follow:
The indicator B may be associated and interconnected with a suitable registering device for registering the number of full and fractional revolutions it makes after the stop H is released. Said indicator and suchregistering device maybe associated and interconnected with a suitable recording device to record the registrations. Suitable means may be employed to instantly return the in dicator, the registering device, and the recording device to a starting position. The indicator B, the registering device and the recording device may be associ ed anc interconnected with a suitable time indicating device, such as a clock, to show the relation of the time intervals to the time of day.
I may employ any suitable type of time interval measuring, indicating, registering and recording means, any suitable electrically or magnetically operated stop release in place of the manually operated release described for actuating the stop H, and other suitable means for varying the current in the telephone circuit to produce th audible signals in the receivers.
lVhile the means employed to vary the current in the telephone circuit is shown connected directly to such circuit at M and N, said means may be connected to said circuit by any other suitable means such as by induction, a link circuit. a telephone iacl: and plug,.or suitable oil and on switch.
Any number of'terminal contacts similar to that shown at O and similarly placedo-n other positions on the dial 0, such as at E, F, and G, and similarly connected to the circuits, may be employed to give signals corresponding to predetermined divisions of the interval of time measured by a full revolution of the indicator B. These contact terminals may vary' as to size of contact surfaces and may be grouped to give several types of signals which can be identified one from the other. The terminal contacts may be so mounted as to be adjustable to difierent operable positions necessary to make contact with the indicator B by suitable means actuated by said indicator and the shaft A in their rotation, to give a different type of signal as the indicator passes a given position on the dial C in successive rotations. Various numbers of telephone receivers may be in the telephone circuit, each providing the audible signals impressed upon the tele phone circuit.
Any other suitable current supply may be substituted for the battery U in Fig. 2, such as A. C. current of any frequency within the audible range, to produce signals in the receivers of desired pitch. Any other suitable electrically actuated sound producing device may be substituted for the bell X shown in Fig. 3.
Combination wire and wireless telephone circuits may be used as well as the wire telephone circuits shown. Operator controlled means may be associated and inter-connected with the indicator B to hold the same sta tionary for periods at any position on the central operators station; an element-nordial C after the indicator starts to rotate from the starting position D, thus increasing the interval of time taken by the indicator to make a full revolution when thus held, sub.- stantially by the length of time such indicator is held,.thus providing a means for subtracting from the time interval a telephone circuit is used, any periods of inoperable interference in the telephone circuit. Means may be provided to give the users an identifiable audible signal in the receivers during the periods when the indicator is held.
The audible signals in the receivers may be of such a nature in respect to their duration, volume, and musical pitch as to cause and yet be distinct. 7
Several of the devices described may be built into one unit, being actuated by the same time measuring means, with which unit one or more operators may time and signal several circuits simultaneously.
What I claim, and desire to secure by Let- 'ters Patent, is:
said member for movement by the latter, releasable-means for holding said element normally against movement during movement of said member,said means being adapted for release to enable said element to move with said member when a circuit is established between a pair of subscribers stations-in the telephone system and when conversation between said stations begins, and means operable by movement of said element to effect signal variations in the current of the subscribers line at predetermined intervals of time. 7
2. In combination with a telephone system including subscribers stations, lines and a mally held against movement and movable at a predetermined rate of speed when released, releasablemeans holding said element normally against movement, said means being adapted for release by the central station operator when an operative circuit has been established between a pair of stations in the telephonesystem, and means under the control of said first named means operable immediately following release thereof to.
simultaneously effect an indication for the operator and a'fsignal variation in the current of said circuit and thereafter to simultaneously repeat said indication and said signal variation following the elapse of pre-' determined periods of time.
In combination with a telephone system including subscribers stations and lines; an element normally held against movement and movable at a predetermined rate of speed when released, releasable means holding said negligible interference withthe conversation element normally held against movement and movable at a predetermined rate of speed when released, releasable means holding said element normally against movement, said means being adapted for release when an operative circuit has been established between a pair of stations in the telephone system, a sound producing device, means under the control of said first named means operable immediately following release thereof to cause said device to produce sound and thereafter to repeat said sound following the elapse of predetermined periods of time, and a transmitter located adjacent to said sound producing device and connected with the subscribers line.
5. In combination with a telephone system including a subscribers line; a shaft rotatable constantly at a fixed rate of speed, an element having a slip connection with said shaft, a releasable stop to hold said element against rotation, said element being adapted to rotate with said shaft when'said stop is released, and means operable by said element immediately following its release to effect asignal variation in the current of said subscribers line and thereafter to repeat said signal variation following the elapse'of pre determined periods oftime.
6. In combination with a telephone system including subscribers stations, lines and a central operators station; means for use by the central station operator to determine a period of use of an operative circuit between a pair of stations in the telephone system, and means under the control of said first named means to effect a signal variation in the current of said circuit at the beginning of said period and to repeat said signal varia tion following the elapse of predetermined periods of time.
7. In combination with a telephone system including subscribers stations, lines and a central operators station; indicating means operable by the central station operator to determine a period of use of an operative circuit between a pair of stations in the telephone system, and means under the control of said first named means to effect and repeat signal variations periodically in the current of said circuit, synchronized with the indications of said indicating means.-
' 1 p 8. In combination with a telephone system
US362693A 1929-05-13 1929-05-13 Method for timing toll telephone circuits Expired - Lifetime US1891594A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US362693A US1891594A (en) 1929-05-13 1929-05-13 Method for timing toll telephone circuits

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US362693A US1891594A (en) 1929-05-13 1929-05-13 Method for timing toll telephone circuits

Publications (1)

Publication Number Publication Date
US1891594A true US1891594A (en) 1932-12-20

Family

ID=23427138

Family Applications (1)

Application Number Title Priority Date Filing Date
US362693A Expired - Lifetime US1891594A (en) 1929-05-13 1929-05-13 Method for timing toll telephone circuits

Country Status (1)

Country Link
US (1) US1891594A (en)

Similar Documents

Publication Publication Date Title
US1889597A (en) Telemetering method and apparatus
US2419487A (en) Remote-control metering system
US1891594A (en) Method for timing toll telephone circuits
US1802643A (en) Electrical meter-reading system
US2007669A (en) Meter reading apparatus
US2326200A (en) Telemetric apparatus
US2035358A (en) Telemetric system and mechanism for use therewith
ES334527A1 (en) Electronic device for automatic indication,registration and forecast of local and distant thunderstorms
US1469056A (en) Reminding device
US558167A (en) Telephone-service register
US843189A (en) Measuring instrument.
US1857593A (en) Tester for watt hour meters and the like
US2202517A (en) Liquid level reporting apparatus
US1707784A (en) Switch device for alarm circuits
US1474053A (en) Telephone meter
US238977A (en) Chronometric signaling apparatus for telephone-lines
US415915A (en) Electrical annunciator
US319718A (en) holcombb
US512413A (en) thomson
US289834A (en) Apparatus
US828000A (en) Fire-alarm system.
US1690269A (en) Testing device
US232156A (en) Peters
US1979998A (en) Telemetering method and apparatus
US774543A (en) Party-line telephone system.