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Publication numberUS2142304 A
Publication typeGrant
Publication dateJan 3, 1939
Filing dateApr 6, 1936
Priority dateApr 6, 1936
Publication numberUS 2142304 A, US 2142304A, US-A-2142304, US2142304 A, US2142304A
InventorsRodney B Cummings
Original AssigneeRodney B Cummings
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
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US 2142304 A
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Description  (OCR text may contain errors)

Jan. 3; 1939. R. B. CUMMINGS I TROUBLE FINDER Filed April 6, 1956 2 Sheets-Sheet 1 6 45M 700 5 C0/WECTED 70 LIME Me:

mm; I

Patented Jan. 3,1939


Application April 6, 1936, Serial No. 73,005

4 Claims. (Cl. 175-183) This invention relates to an improved method -for locating trouble such as accidental grounds or short circuits in alternating current light and power systems, or telephone lines, and comprises portable equipment and its use as will hereinafter appear from the specification.

Heretofore, sundry methods and apparatus have been employed by repair men for locating faults in line wires. Usually an exploring coil was used in combination with an ordinary hand generator, the test man shifting the exploring coil from one side of the test lead to the other or else the leads were shifted on the wires. By this invention such shifting is not necessary and.

the generator is not' used. Instead a device hereinafter referred to as a cable tone is connected to the line wires and cooperates with the exploring coil.

The object of the invention is to provide simple and positive means for the location of faults in circuits, principally those carrying telephone or telegraph circuits.

A further object is the provision of apparatus, which is portable, sensitive and reliable in action for locating line troubles.

A further object of the invention is the provision of means for temporarily connecting a telephone set to the lines.

With the foregoing and other objects in view, as will hereinafter appear, this invention comprises the constructions, combinations and arrangement of parts, hereinafter set forth as described and shown.

Inthe drawings wherein similar numerals indicate similar parts:

Figure l is a View of a pair of lines, to which the detecting and testing device in accordance with the invention is associated.

40 Fig. 2 illustrates the method of connecting a cable tone to line wires where the wires are short circuited.

Fig. 3 illustrates a similar connection where two lines-are grounded.

45 Fig. 4 illustrates another application of the cable tone.

Fig. 5 illustrates a view of the support rod taken on line 5-5 of Fig. 1 in the direction of the arrows.

50 Fig. 6 illustrates the exploring coil mounting means in the support rod.

Fig. 7 shows a schematic arrangement of the cable tone.

Fig. 8 shows a schematic arrangement of the 55 impulse receiving apparatus.

Fig. 9 is a showing of the cable tone connected to the line.

Fig. 10 shows the support rod alone.

Fig. 11 shows the exploring coil mounting.

Fig. 12 shows a line connector. 5

In the broad aspect of the invention an oscillating current is transmitted from the cable tone through the lines to be tested and back to the cable tone. An exploring coil when shifted along the wires but out of contact therewith will pick lb up by induction a small amount of current when in the path of the current emanating from the cable tone. The exploring coil is mounted on a support rod and connects with an amplifier and a sound transmitter and constitutes the pick-up 6 device. As is readily apparent an amplified-signal will be received at the transmitter wherever the cable tone current is-flowing, so that the operator may easily trace the path of the current to the trouble source. 20

Referring to Figure l the transmission lines it and 2 are shown connected to a source 3 of alternating current for testing purposes, this source being hereinafter referred to as a cable tone.

Out of physical contact but inductively coupled 26 to these tested lines is an exploring coil l2 mounted on a telescoping type of support rod 8. Electrical connections from the exploring coil extend through the rod 6 to a socket it, through a plug l5, line it, to an amplifier ll, through line 30 it to a sound transmitter l9, in this case a head set being illustrated.

The cable tone is more particularly illustrated in Fig. 7 wherein an electromagnetic coil is connected across a D.- C. source of E. M. F. 35 and vi- 35 brating contacts 33. An armature 3t actedon by the coil 36 intermittently makes and breaks the contacts 33. Terminal leads ill and 38 are connected across the coil 36 and are joined to the lines l and 2 as shown in Fig. l. A bell 43 is connected to the terminal lead 38 and to ground at M. A blocking condenser at of 0.5 mmf. is placed across terminal leads Bl and 38. This condenser acts as a by-pass for undesirable high frequency currents that would tend to pass from 45 the cable tones into the lines.

In the modified form of the cable tone in Fig.

9 a wave trap comprising inductances All and M and condenser $2 is interposed between the cable tone and lines to eliminate undesirable frequencies from reaching the lines. The condenser may be located at either end of the inductan'ces.

An exploring coil 52 found to produce very good results is one made from a model T-Ford ignition coil. In this instance the two secondary 58 coils are connected in series. However, such exploring coil may also be made by other methods well known in the art. The coil I2 is supported by a hollow insulating rod l3 having two longitudinally displaced electrical contacts 22 and 23 which are connected to the wires of the coil. Contact 22 is of larger diameter than 23 to facilitate insertion into the support hood. In contact 22 is a bayonet pin to engage a bayonet slot 5| (see Fig. 10)

The support rod comprises two tubular elements 6 and 1 preferably of insulation and mounted in adjustable telescoping relation by sleeves 8 and 9 (see also Fig. 5). Sleeve 8 is secured at 28 to rod member 1 and slides over element 6. Sleeve 9 is similarly secured to the element 6. A set screw in one or both sleeves 8 and 9 serves to hold elements 6 and l in fixed position.

In Fig. 6 contacts 25 and 26 are set in insulating bases as shown at In and II respectively of the support rod 6 and electrically contact the conducting elements 22 and 23 of the exploring coil. Contact 25 has a larger diameter than contact 26 to correspond with the enlarged contacts 22 and 23 or 46 and 41 of the detachable elements. Contact 25 has a bayonet slot 5! to receive bayonet pins 50 for locking engagement. The detachable element Fig. 11 or 12 is inserted vertically then rotated for locking movement or engagement.

Wires 20 and 2| lead from contacts 25 and 26 through openings 21 into the tubular element 6 to contacts in socket l4 'at the lower end. The electrical contacts in socket l4 may each, as illustrated in Fig. 10, be connected respectively with one of the contacts at 29 and 30 for a purpose to be later described.

Plug l5 connects the exploring coil with an amplifier device through conductor cord IS. The exploring coil may be coupled to any emcient amplifier with as'rnany stages of amplification as desired, and may be resistance coupled or transformer coupled. The output of the amplifier feeds into a receiver l9 such as high impedance headphones or a loud speaker.

Fig. 8 illustrates the wiring scheme from the exploring coil to the headphones corresponding to Fig. 1. r

In Fig. 2 the lines are shown short circuited at 4 while in Fig. 3', both lines are shown grounded.

In Fig. 4 is shown the cable tone connected to one of the lines I and the bell connected to ground 44. This bell is thus in the tone circuit so that a lineman out' in the line somewhere may signal an attendant at the cable tone by connecting an ordinary linemans portable telephone (magneto type) from one side of-the line to the ground; and by turning the generator, the bell will ring if the trouble in the line is cleared or is of such a nature that a circuit can-be completed to the bell through ground and one side of the line. The bell used is or the ordinary telephone typeand has at least the impedance of such type bell to avoid inter- Ierence with the proper operation of the tone circuit.

With the cable tone thus connected to the transmission lines the bell is connected to ground from the side of the line I am testing, I may call in on this side of the line, even with the tone connected to signal an attendant at the oflice. This method does not tie up the circuit when the ,cable tone is connected.

In Fig. 10 the support rod is shown disconnected from the exploring coil and amplifier. It also illustrates better the. contacts 25 and 26, the insulating elements I0 and II being purposely omitted forthis reason. The openings 21 for the wires from the contacts to the tube interior is also "two spring clip electrical'contacts 3| and 32 at the ends. An insulating hollow support 48 extends at right angles and centrally of spacer 45. On this support 48 are longitudinally displaced contacts 46 and 41 similarly arranged and constructed at 22 and 23 in the exploring coil unit. Wires concealed in parts 45 and 48 connect contacts 3| to 41 and 32 to 46. It can be readily seen that either the line tapper or the exploring coil may be quickly mounted or dismounted from the support rod.

Where the line tapper is applied to the support rod a telephone set well known in the art may be. connected with electrical contacts 29 and 30 in the support rod and electrically connect with lines I and 2 through spring clip contacts 3| and 32.

When trouble appears in the lines the cable tone 3 is connected with the lines and an oscillating current sent therefrom over the lines. Such current will travel in the paths shown in any of the Figures 2 to 4 and 9.

The detecting equipment including the exploring coil, amplifier, speaker or headphones, and

the connections may all be carried in an automobile or other vehicle. The exploring coil may be placed any reasonable distance from the lines and moved by the vehicle along the direction of the lines. The amplifier serves to amplify considerably the signal receiver from the lines. When the coil is moved along the lines a point will be reached where no signal or a faint signal is obtained, theindication that the end of the current path has been reached. At such point it will be found that the wires are short circuited, or one or both wires are grounded.

For carrying on a conversation the line tapper 30 is inserted in the support rod and a telephone is connected at 29 and 30.

Having thus described my invention, I claim:

1. In an inductive coupler for testing transmission lines the combination of an exploring coil, an amplifier and signal receiver, of a supporting rod interposed between the exploring coil and amplifier, said rod comprising two longitudinally adjustable members at least one of which is hollow, means for holding the members in adjusted relation, two insulated contacts on one of the members adapted to detachably receive ,placed contacts on said support of similar configuration but of dissimilar cross-sectional area and connection means between each contact and coil within the support.

3. A support for an exploring coil comprising relatively longitudinally adjustable rod members, adjustable clamping means thereon, insulating contacts at the upper end of one rod member,

there being two sets of contacts at the lower end amasos 3 the respective extension contacts and the spring contacts, said adjustable support including relatively longitudinally adjustable tubular members,- longitudinally spaced insulated contacts on one member to receive those on the extension, and

conductors extending into the tubular member from the support contacts.


Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2475680 *Mar 14, 1946Jul 12, 1949Union Switch & Signal CoTest equipment for faulty electrical insulators
US2586781 *Oct 11, 1948Feb 26, 1952Phillips Petroleum CoLine fault detector
US2595623 *Feb 28, 1950May 6, 1952Radio Frequency Lab IncSignal generator
US2615969 *Apr 15, 1949Oct 28, 1952Albrecht Esther VElectrical power line warning device for vehicles with extended booms
US2698921 *Jun 11, 1948Jan 4, 1955Donald A WhartonTesting instrument
US4095212 *Jun 27, 1977Jun 13, 1978Billy Paul PruittRemote electric state tester
US4439723 *May 11, 1981Mar 27, 1984Loftness Marvin OUltrasonic and VHF locator of electrical systems defects
DE1017277B *Sep 3, 1954Oct 10, 1957Fruengel Frank Dr IngEinrichtung zur Ortsbestimmung von Kabelfehlern mit Hilfe eines Pruefwechselstromes mit hoerbaren Frequenzanteilen
U.S. Classification324/529, 324/537
International ClassificationG01R31/08
Cooperative ClassificationG01R31/08
European ClassificationG01R31/08