Telephone line test kit

An electrical test kit for testing a telephone line from the terminals at the customer's end of the line includes a circuit for testing line continuity without falsely indicating to the voltage source that a telephone call has been answered, a push-button selection switch and a parallel pair of light-emitting diodes connected in reverse polarity relative to each other for determining polarity of the telephone line, and test pads in parallel with the continuity test circuit for permitting the attachment of a voltmeter so as to determine the magnitude of the internal resistance of the telephone line.

FIELD OF THE INVENTION 
This invention relates to test devices for electrical circuits, and 
particularly for use with telephone or other voice communication circuits. 
BACKGROUND OF THE INVENTION 
There is a great deal of need for convenient test devices to test telephone 
circuits or other voice communication circuits. Such devices typically 
will measure circuit continuity, proper polarity, and other factors 
pertinent to the proper operation of the circuitry. Typically the device 
is in the form of an elongated connector that may have both of its ends 
temporarily connected to a circuit to be tested. Typically, such a device 
may be interposed in series in the circuit for in-line testing, by 
connecting it between the wall jack and a telephone. 
For data circuits a "straight-through connection" may be used for the 
conductors inside the connector, and pin 1 of the jack at one end is then 
electrically connected to pin 1 of the jack at the other end. Voice 
circuit testing, however, is best accomplished with a connector that is 
"reverse-wired", meaning that pin 1 of the jack at one end is connected to 
the highest numbered pin of the jack at the other end, which is typically 
pin 6. 
Alternatively, as is also well known, such a device may be used by 
connecting only one of its ends to a circuit to be tested. For example, it 
is connected to a telephone jack to test an incoming telephone line. One 
parameter of great interest is the "tone" that exists when the normal 
direct current driven by a 24 volt source is flowing through the telephone 
line. Another parameter of interest is the signal loss that occurs as a 
result of the electrical resistance in the customer's line extending from 
the central office. 
Since many different parameters and conditions may be tested, there is 
always a need for test devices that are versatile in their capabilities 
but are at the same time easy to use, inexpensive, and reliable. 
SUMMARY OF THE PRESENT INVENTION 
The present invention provides an electrical test kit for testing a 
telephone line from the terminals at the customer's end of the line to 
simultaneously test continuity, polarity, tone or line voltage received 
from the telephone central office or other voltage source, and line 
resistance. Alternatively, the test kit may be used for in-line testing 
while the circuit remains in operation. 
One component of our novel test kit is a circuit box that contains contacts 
connectable to a telephone jack; and a series loop circuit, controlled by 
a push-button switch, that contains light emitting diodes for indicating 
circuit continuity, line voltage, and polarity of terminals. This circuit 
box is also provided with breakout test pads that allow access to the 
circuit being tested without disrupting service. 
A second component of our novel test kit is a standard voltmeter, used in 
conjunction with the push-button circuit and the breakout pads to 
determine whether the resistance in the telephone line leading to the 
customer's premises is within allowable limits.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Referring now to FIG. 1, an electrical test kit for testing a telephone 
line from the terminals at the customer's end of the line includes a 
circuit box 20 and a standard D. C. voltmeter 40. The telephone company 
central office is indicated at 10, and the line to the customer's premises 
at 12. A wall jack in the customer's premises is designated as 14, having 
terminals 16, 17. 
Circuit box 20 includes a pair of contacts 22, 23 adapted to be temporarily 
connected to the corresponding terminals 16, 17 of the wall jack. A test 
circuit connected in a series loop between the contacts 22, 23 includes a 
push-button switch 32, a resistor 30, and a parallel pair of 
light-emitting diodes 33, 34. The diodes are connected in reverse polarity 
relative to each other, so that when the push-button switch is closed the 
lighting of either of the LEDs will indicate both the presence of line 
voltage and circuit continuity. Furthermore, the particular LED that is 
lighted will indicate the polarity of the terminals 16, 17. 
The purpose of our test kit is to simultaneously test continuity, polarity, 
line voltage received from the telephone company office or other voltage 
source, and line resistance of the line leading to the customer's 
premises. 
The resistance value of the resistor 30 is chosen in the range of about 
three to ten thousand ohms so that the temporary connection of the test 
circuit to the telephone terminals will not falsely indicate to the 
switchboard at the telephone company office that a telephone call has been 
answered by taking a telephone off hook. Preferably the value of resistor 
30 is 6.8k ohms. 
The circuit box 20 also a pair of metal breakout test pads 24, 25 which are 
connected to respective ones of the contacts 22, 23. The voltmeter 40 may 
be connected by means of standard alligator clips to the test pads 24, 25 
for providing a voltage reading that indicates the magnitude of the line 
resistance from the source to the terminals of the telephone jack. For 
example, if the voltmeter indicates 24 volts, the line resistance is 
negligible and very acceptable. On the other hand, if the voltmeter 
indicates only 12 volts or less, the line resistance is considered 
excessive, and the customer is not being adequately served because too 
much signal will be lost in transmitting messages to his telephone 
instrument. 
FIG. 2 shows schematically the full circuit inside the circuit box 20. As 
shown in FIG. 2 the circuit box 20 has jacks J1 and J2 at its respective 
ends, which are of the RJ12 type. Each has six pins numbered 1 through 6, 
inclusive. Internal wiring of the circuit box is such as to connect pin 1 
of one jack with pin 6 of the other, and so on. 
Also included in circuit box 20 are metal test pads W1 . . . W6, inclusive. 
Each is connected in series with a respective conductor inside the box. 
For example, test pad W1 is connected in series with two separate parts 
27, 28 of a conductor that connects pin 1 of jack J2 with pin 6 of jack 
J1. 
In a six-wire telephone cable, a common practice is to arrange wires 2 and 
5 as a pair, and 3 and 4 as another pair. Wires 3 and 4 correspond to the 
example of FIG. 1. That is, wire 3 of jack J2 and wire 4 of jack J1 
connected to test pad W3 are also connected through a Ring Line 1 to a 
push-button switch S 2, and to a resistor R1 that has a resistance value 
of 6.8 kilohms and is rated at 0.5 watt power dissipation. A pair of 
light-emitting diodes D3 and D4 connected in parallel but in reverse 
polarity to each other are then connected between the other end of 
resistor R1 and test pad W4, which is connected to wire 3 of jack J1 and 
wire 4 of jack J2. This is the same circuit as described in conjunction 
with FIG. 1. 
The circuit box 20 includes another identical circuit, in which switch S1, 
resistor R2, diode pair D1/D2, and Ring Line 2, are connected in a series 
loop to wires 2 and 5 of the cable. 
FIG. 3 shows the preferred manner of mechanizing the push buttons. As 
schematically shown there, a single push bar B is attached to both of the 
push buttons for actuating both of them simultaneously. This makes it 
possible to test two circuits at the very same time. 
The important advantage of our invention is its extreme versatility--that 
is, the circuit box may be used alone or in conjunction with the test pads 
and voltmeter for in-line testing. 
It may also be used either alone or in conjunction with the test pads and 
voltmeter for testing simply from the end of the customer's phone line. 
The operator may depress one or both pushbuttons at the same time that the 
voltmeter reading is being observed. 
The presently preferred form of the invention has been disclosed in detail 
in order to comply with the patent laws. However, the scope of the 
invention is to be judged only in accordance with the appended claims.