GB2105050A - Improvements in and relating to circuit testing apparatus - Google Patents

Abstract

In the automatic testing of electrical or electronic circuits via pins (1, 2...30) test signals may be applied to points in e.g. a logic circuit to be tested, the signals preferably being applied for such short periods of time as not to damage components in the circuitry. High speed switches (HSS), preferably electronic, are individually enabled so as to pre-select particular pins (1, 2 . . .30), and a pulsed voltage source (270) then momentarily energises these pins. Output signals are read by energising one of three relay coils (168, 170, 172) each of which connects all the pins of a respective group (e.g. pins 1 to 10) to output lines (71, 72...80). One of these lines is then selected by a switch (150). Control means (154) controls and switches (HSS) in accordance either with pre-stored information or with information specially generated (if no pre-stored information is located for the particular circuit to be tested). In the latter case, the specially generated information is stored so as to be available when that particular circuit is next tested. <IMAGE>

Description

SPECIFICATION Improvements in and relating to circuit testing apparatus The invention relates to methods and apparatus for the automatic testing of electrical and electronic circuitry. More specifically, it may relate to testing such circuitry in integrated form. For example, the methods and apparatus to be more specifically described below can be used for applying test signals to integrated logic circuits and to determine, from the resultant outputs produced by the logic circuits, whether the logic circuits are operating correctly and, if not, which part is faulty.

Various novel features of the invention will be apparent from the following description, given by way of example only, of automatic test apparatus embodying the invention, reference being made to the accompanying diagrammatic drawings in which: Figure 1 is a block circuit diagram of part of the apparatus; Figure 2 is a schematic circuit diagram of some parts of the apparatus of Fig. 1; and Figure 3 is a block diagram of part of the apparatus.

The apparatus to be described is for the automatic testing of electrical and electronic circuitry, and may comprise: a plurality of contact means mounted in predetermined physical relationship with each other for making electrical contact with predetermined points on circuitry to be tested; a plurality of switching elements each connected to a respective one of the contact means and each capable of being operated to feed to the contact means signals to be applied thereby to the circuitry under test or to feed from the contact means output signals produced by the circuitry under test; control means for operating the switching means; means for storing, for each of a plurality of separately identifiable circuits to be tested, test information defining a respective sequence of test signals to be applied to predetermined terminals of that circuit and the resultant output which should be produced at one or more predetermined terminals of the circuit if it is operating correctly; input means for identifying a particular circuit to be tested and for feeding the said test information relating to that particular circuit out of the storage means; means for generating connection information correlating the particular predetermined terminals of that circuit with the particular contact means to which those terminals are temporarily concected; and programming means responsive to the fed out test information and the connection information so as to set the control means to operate accordingly; whereby the control means applies one or more predetermined test signals to the particular predetermined terminals of circuit under test and measures any resultant signal produced by the circuit under test at the particular predetermined terminal or terminals so as to assess whether the operation of the circuitry is faulty or not.

Advantageously, the apparatus includes means for entering into the programming means test information relating to a circuit to be tested for which test information is not stored in the storage means, means for entering into the programming means connection information relating to that circuit, and means for feeding into the storage means the said test information and identifying it as relating to the particular circuit so as to enable it to be read out when that circuit is next to be tested.

In a more specific sense, there is shown and described apparatus for the automatic testing of electrical and electronic circuitry comprising: a plurality of contact means mounted in predetermined physical relationship with each other for making electrical contact with predetermined points on circuitry to be tested; a first plurality of switching elements each connected to a respective one of the contact means and each capable of being set into a first state or a second state by means of enabling signals; means for energising the switching elements; means for applying momentary control signals to all the switching elements in common whereby each switching element in the first state feeds a momentary test signal of first predetermined level to its corresponding contact means and each switching element in the second state feeds a momentary test signal of second predetermined level to its corresponding contact means; each switching element not in the first or second state not affecting its corresponding contact means; a second plurality of switching elements interconnected with the contact means and settable by means of setting signals to select at least one of the contact means; and control means for generating the enabling signals and the setting signals in accordance with information relating to the particular circuitry under test whereby to apply one or more test signals at respective said predetermined levels to particular parts of the circuitry and to measure any resultant signal produced by the circuitry under test at the contact means selected by the second switching elements, so as to assess whether the operation of the circuitry is faulty or not.

The duration of each said momentary control signal is arranged to be such, in relation to the said predetermined levels, that the test signals applied to the circuitry do not damage the components thereof.

The switching elements of at least the first plurality may be electronic switching elements.

The switching elements of the second plurality may be electromechanical relays.

The switching elements of the second plu rality may comprises at least two groups of switching elements, each switching element of a first one of these groups connecting a respective one of a first group of the contact means with a respective one of a plurality of lines corresponding in number to the number of switching elements and contact in the first group, and each switching element of the second group connecting a respective one of a second group of the contact means to a respective one of the said lines, and a further switching element for selecting any particular one of the said lines, the switching elements of the first group being ganged for operation together and the switching elements of the second group being ganged for operation together; whereby any particular one of the contact means can be selected by the setting signals by operating the switching elements of the particular group associated with the group of the contact means in which the particular contact means lies, so as to connect that particular contact means to its respective one of the said lines, and operating the further switching element to select that particular one of the lines.

Advantageously, the apparatus includes means for storing for each of a plurality of separately identifiable circuits to be tested, test information defining a respective sequence of test signals to be applied to predetermined terminals of that circuit and the resultant output which should be produced at one or more predetermined terminals of the circuit if it is operating correctly, input means for identifying a particular circuit to be tested and for feeding the said test information relating to that particular circuit out of the storage means, means for generating connection information correlating the particular predetermined terminals of that circuit with the particular contact pins to which those terminals are temporarily connected, and programming means responsive to the fed out test information and the connection information so as to set the control means to operate accordingly.

Advantageously, the apparatus includes means for entering into the programming means test information relating to a circuit to be tested for which test information is not stored in the storage means, means for entering into the programming means connection information relating to that circuit, and means for feeding into the storage means the said test information and identifying it as relating to the particular circuit so as to enable it to be read out when that circuit is next to be tested.

The foregoing are exemplary of and not exhaustive of the various features of the apparatus now to be described in detail.

The apparatus now to be more sepcifically described is, in this example, intended for testing the operation of integrated logic circuits and other circuit elements such as resistors and capacitors. For testing a logic circuit testing is carried out by applying predetermined test signals (such as representing binary levels that may arise in the logic circuit during its normal operation) to the relevant points in the logic circuit, and monitoring the resultant outputs by comparing them against the outputs that should arise if the circuit is operating correctly-so as to indicate a fault (and the position of the fault) if an incorrect, or no, output is produced.

The test signals may be applied to the logic circuit by means, for example, of a contact plate having a plurality of contact pins (which may be spring loaded) which are so physically arranged in relation to each other that, when the contact plate is placed adjacent to the circuit board carrying the logic circuit to be tested and held by a suitable jig, the pins are pressed into firm electrical and mechanical contact with those points in the logic circuit to which test signals are to be applied. This means, of course, that each test signal will not only be applied to the input of the particular logic circuit which it is intended to test, but will also be applied to the output of the immediately preceding part of the total circuit.

In order not to cause damage to the electronic components (for example, the transistors) of this preceding part, the test signals are applied for not more than a predetermined length of time (say 10 uS) which is selected so that the electrical heating or any other effect which it causes is not sufficient to result in any damage to those components.

Figure 1 shows, diagrammatically, the contact plate P from which project thirty (in this example) contact pins which are spring loaded, electrically insulated from each other, and have sharp points so as to make good electrical contact with the respective parts of the circuitry to be tested when the contact plate and the circuit board carrying the circuitry are mounted together in a suitable mounting jig so as to have a predetermined relationship to each other. The pins are numbered 1 to 30. In a manner to be explained, the pins are electrically arranged in three groups of ten, and in order to save space in the Figure only the first two and the last pins of each such group are shown in the Figure, these pins therefore being numbered 1, 2 and 10, 11, 12 and 20, and 21, 22 and 30.

Each pin has associated with it a respective screen 1A, 2A, 3A. . . , and these screens are all connected electrically together and thence to ground by means of a line 32.

The system also includes thirty high speed switches (HSS), one for each contact pin. The HSS are numbered 41 to 70 and each has a respective output line A which connects it to its respective contact pin; in the drawing, only the HSS 41, 42 and 50, 51, 52 and 60, and 61, 62, and 70, are illustrated, together with their respective output lines.

The ten contact pins 1 to 10 of the first group are also connected via respective relay contact pairs 101 to 110 to ten lines 71 to 80 As shown, the contact pins 11 to 20 of the second group of pins are also respectively connected to the output lines 71 and 80, in parallel with the contact pins 1 to 10 of the first group, via respective relay contact pairs 111 to 120.

Similarly, the contact pins 21 to 30 are respectively connected to the output lines 71 to 80, in parallel with the contact pins 1 to 10 and the contact pins 11 to 20, via respective relay contact pairs 121 to 130.

The lines 71 to 80 are respectively connectable by means of a selector switch 150 to a line 152 which connects to the central control unit 154 of the system. The switch 150 is set to any particular state by means of setting signals received on a line 155 from the unit 154. The switch 150 may in fact comprise respective pairs of relay contacts between each of the lines 71 and 80 and the single line 152, a particular one of the relay contact pairs being closed (under control of the setting signals on line 155) in order to determine which of the output lines 71 to 80 is connected to the single line 152.

The relay contact pairs 101 to 110, 111 to 120, and 121 to 130 are controlled by a control circuit 160. This circuit comprises three transistors 162, 164 and 166 in each of whose collector circuits is connected a respective relay coil 168, 170 and 172. The collector circuits of the transistors are connected in common to a ground line 174, while their emitters are connected to a positive supply line 176. Each transistor may be rendered conductive by a setting signal applied to its base via a respective pin 178, 180 and 182 and via respective diodes 184 and resistors 186, and when so rendered conductive the transistor energises its respective relay coil. Energisation of relay coil 168 closes the contact pairs 101 to 110; energisation of relay coil 170 closes relay contact pairs 111 to 120; and energisation of relay coil 172 closes relay contact pairs 121 to 130.The lines 178, 180 and 182 are controlled by the central control unit 154 but their connections to unit 154 have been omitted for clarity.

The HSS will be described in detail below.

However, each has a respective pair of enabling lines B and C. The enabling lines B and C of all the HSS are connected individually to the central control unit 154 by means of connections which have been omitted from the drawing for clarity.

In addition, all the HSS are connected to a common control line D which is fed from a pulsed voltage source 270 in the central control unit 154. Finally, the HSS are all con nected in common via unit 271 to lines E, F and G which are fed from a voltage supply source 272 to be described in detail below.

The source 272 is controlled by the control unit 154 via line 273 and holds line E at the level of a binary HIGH signal for the logic circuit to be tested (which may, for example, be between + 3 volts and + 30 volts depending on the type of logic involved). Line F is connected to the ground line 174, while line G is held at, say, + 5 volts.

When the enabling line B of an HSS is ON (and enabling line C OFF), then the respective output line A goes to the binary HIGH level of line E when, and for so long as, the control line D is pulsed ON by the pulse source 270.

When the control line D goes OFF, the output line A reverts to a floating level, at which it can assume a potential as determined by the logic circuit under test (in other words, it does not affect the logic circuit under test).

When the enabling line B is OFF and the enabling line C is ON instead, then the output line A of the HSS is switched to the binary LOW level of line E when and for so long as the control line D is pulsed ON by the pulse source 270. When the control line D goes OFF again, then the output line A reverts to the floating level mentioned above.

When neither of the enabling lines B and C is ON, then the output line of the HSS is continuously unaffected by pulsing of the line D and remains at a floating level.

In this way, the central control unit 154 can set up each of the HSS individually, by applying appropriate ON and OFF signals to thier enabling lines B and C, so that, when the control line D is pulsed ON, the output lines A of the HSS apply desired binary levels to their corresponding contact pins 1 to 30.

The pulse source 270 may be arranged so as to provide ON pulses having a length of, say 10 uS In this way, the HSS can apply binary input levels to various parts of the logic circuit under test.

In operation, not all the contact pins 1 to 30 would be used to supply binary input signals to the logic cicuit under test; at least one contact pin would be used to feed out the resultant binary output signal from the logic circuit to the central control unit 154 for determining whether or not the logic circuit is operating correctly. The HSS of this contact pin would therefore not be enabled by its lines B and C.Instead, this contact pin would be selected (via lines 178, 180 and 182) by energising the particular relay coil 168, 170 and 172 corresponding to the particular group of ten contact pins in which the particular contact pin lies, so as to connect that particular contact pin to its respective one of the output lines 71 to 80, and then selecting (via line 155) that particular output line by means of the selector switch 150 as to connect it, by means of the single line 152, to the central control unit 154.

The circuit diagram of one of the HSS will now be described in more detail with refer ence to Fig. 1; the remaining HSS have identical circuits. Fig. 2 also shows, connected to the HSS, the circuit diagram of the connection unit 271; there is only one such connection unit which is connected to all the HSS in parallel and connects them to the pulse source 270, the voltage source 272 and the central control unit 154.

The HSS comprises a section 300 which is controlled by the enabling line B and determines whether the output line A of the HSS goes to binary HIGH when the line D is momentarily pulsed from negative to positive voltage (according to whether the enabling line B is ON or OFF), and a section 302 which is controlled by the enabling line C and determines whether the output line A goes to binary LOW when the line D is momentarily pulsed from negative to positive (according to whether the enabling line C is ON or OFF).

Section 300 comprises an npn transistor 304 whose emitter-collector path is connected between the line D and the line F via a resistor 306. The base of this transistor is connected to the enabling line B via a resistor 307. Transistor 304 has a capacitor 308 connected across it together with a resistor 310, and the base-emitter path of an npn transistor is connected across resistor 310 via a resistor 314. The collector of transistor 312 is connected to the line E via a resistor 316, across which is connected the base-emitter path of an output transistor 318 whose collector is connected to the outline A of the HSS.

A large capacitor 320 is connected between lines E and F.

The section 302 comprises an npn transistor 322 whose emitter-collector path is connected between lines D and F via a resistor 324, and the base of this transistor is connected to the line C via a resistor 325. A capacitor 328 is connected across transistor 322, and the base-emitter path of a further transistor 330 is connected across this capacitor via resistors 332 and 334. The collector of transistor 330 is connected to the line G. The base of an output transistor 336 is connected to the junction between resistors 332 and 334, and the emitter of this transistor is connected to line F. Its collector is connected to the output line A of the HSS. A capacitor 338 is connected between line G and line F.

In operation, line D is normally at zero volts, and, when both of the enabling lines B and C are OFF, each is held relatively positive so that both transistors 304 and 322 are conductive. In the section 300, therefore, transistors 312 and 318 are non-conductive, and in the section 302 transistors 330 and 336 are likewise non-conductive. The output line A is therefore at a floating potential which is determined by the conditions in the logic circuit under test.

When line D is pulsed momentarily positive, conditions in the HSS do not change, because the conducting transistors 304 and 322 hold the bases of transistors 312 and 330 at zero volts.

However, when the enabling line B is ON (and enabling line C is OFF), line B is at zero volts, and therefore transistor 304 becomes non-conductive. For so long as line D remains at zero volts transistors 312 and 318 remain non-conductive and the output line A therefore remains at the floating level. However, when line D is momentarily pulsed relatively positive, transistor 312 conducts and switches on transistor 318 which therefore connects the output line A to the binary HIGH logic level of the line E. at the end of the pulse an line D, transistor 312 and 318 switch off again, and line A once more reverts to the floating level.

If the enabling line C is ON (and enabling line B is OFF) instead, then line C is held at zero volts and transistor 322 is switched off.

Again, for so long as line D remains at zero volts, transistors 330 and 336 remain nonconductive and line A remains at the floating level. However, when line D goes momentarily positive, transistor 330 conducts and switches on the transistor 336, which therefore switches the output line A to the binary LOW level of line F.

In the connection unit 271, line E is connected to the voltage source 272 via a pair of relay contacts 352, terminals 353, and current limiting means 354 of any suitable form.

Line F is connected to the voltage source 272 via a relay contact pair 355, a line 356 and a terminal 357. Line 356 is connected to a terminal 358, which is held at + 24 volts, via two parallel-connected relay coils 360 and 362, and the emitter-collector path of a transistor 364, the base-emitter path of transistor 364 being connected across a resistor 366.

Relay coil 360 controls the contact pair 352, while relay coil 362 controls the contact pair 355.

Line G is connected to a + 5 volt supply of source 272 via terminal 370 and a resistor 372, and this resistor also supplies a field effect transistor 274 whose source is connected to the line D and whose gate is controlled via a resistor 376 and a terminal 378 connected to the pulse source 270.

When the system is switched on, a zero volt level at terminal 358 causes transistor 364 to conduct, thus energising the relay coils 360 and 362. Relay contact pairs 352 and 355 conduct, and line F therefore becomes connected to the voltage sorce through contacts 355 and terminal 357. Similarly, relay contact pair 352 connects line E to the logic level (for example, between + 3 volts and + 30 volts) determined by the central control unit 154 in accordance with the type of logic of the logic circuit under test. The current limiting means 354 prevents too large a current when the system is initially switched on the charging current flows into the large capacitors of each HSS. Line G is permanently connected to a positive level via resistor 372.

Terminal 378 is normally held at such level by the pulse source 270 that the FET374 is non-conductive and line D is therefore held at zero volts. However, when the pulse source 270 momentraily pulses terminal 378, the FET conducts and line D goes relatively positive.

A large resistor 380 is connected between line 356 and the gate of the FET 374 so as to hold line D at zero volts should the terminal 378 be inadvertently disconnected.

Fig. 3 shows, diagrammatically, how the central control unit 154 is itself controlled in accordance either with pre-stored test information corresponding to one of a plurality of different predetermined logic circuit types, or, where a logic circuit to be tested is not one of the plurality, in accordance with instructions from the operator. In the latter case, in a manner to be described, the instructions fed in by the operator are arranged to be stored and identified so that they can be called up again when that particular type of logic circuit is next to be tested, merely by identifying that logic circuit.

In Fig. 3, items corresponding to items in Figs. 1 and 2 are correspondingly referenced.

The circuitry comprising the HSS, their output lines A, the lines 71 to 80, and the selector switch 150 is shown in a single block 400, while the contact plate bearing the contact pins 1 to 30 is represented by block 402 and a circuit board including the logic circuit to be tested is represented by block 404.

The system includes a store 406 which stores test information relating to a plurality of different predetermined types of logic circuit.

Thus, for each of the logic circuits, it stores information which defines the binary output level (or levels ) which should be produced on one (or more) terminals if the logic circuit is operating correctly for each of a plurality of different predetermined binary input levels on other terminals of the logic circuit. The terminals are identified by serial numbers (e.g.

numbers 1-14) in accordance with standard numbering.

The operator is then provided with a keyboard 408 by means of which he may generate a test programme for the logic circuit, or combination of logic circuits, by defining the type numbers of the logic circuits. Signals representing these type numbers are then fed to the programmng unit 41 8 by means of a channel 410, an input/output unit 412 and a channel 442.

When the operator has fed in the type number of the logic circuit to be tested, he then has to feed in connection information to identify the particular contact pins on the contact plate 402 which correspond to the terminals of the particular logic circuit that he wishes to test on the circuit board 404. For example, if the logic circuit to be tested is of a type which has fourteen terminals numbers 1 to 1 4, and these terminals happen to be so physically positioned on the circuit board 404 as to be respectively contacted by contact pins 2, 4, 5, 6, 7, 12, 15, 17, 18, 23, 26, 27, 28, and 30, the operator would use the keyboard 408 to insert, sequentially, these fourteen numbers in that order. Signals corresponding to these numbers are fed by means of a channel 410, the input/output unit 412 and a channel 422 to the programming unit 418.

The programming unit 418 then compares the type number of the logic circuit with the plurality of logic circuits for which test information is stored in the store 406, and then using the predetermined test information stored on the store 406 and the connection information provided by the operator, it feeds out the information in terms of the appropriate contact pins on the contact plate 402 instead of in terms of the actual terminal numbers of the logic circuit. Therefore, the programming unit produces, for that logic, a sequence of test patterns, each test pattern comprising information defining the binary levels which are to be applied to certain of the contact pins 1 to 30 on the contact plate 402 (via the HSS) and the binary output level that should be produced on another one (at least) of the contact pins 1 to 30 if the logic circuit is not faulty.These sequences are fed to the store 422 on channel 423.

A display unit 424 is provided, and by means of this, and channels 426 and 428, the programming unit 418 may signal to the operator that the logic circuit which the user wishes to test, and which he has identified on the keyboard 408, is in fact the logic circuit for which test information is already in the store and that the test sequence has been generated and stored.

Testing can now be carried out under control of the information stored in the store 422.

Under control of channel 429 the central control unit 154 energises appropriate ones of the enabling lines B and C, which are shown connected between the central control unit 154 and the block 400 by a channel 430, and then energises an appropriate one of the control lines 178, 180 and 182, and so sets the selector switch 150 by means of the line 155, that the particular one of the lines 71 to 80 which is connected to the contact pin on the contact plate 402 where the binary output is to be produced is connected back to the central control unit 154 by means of the line 152.

The central control unit 154 then energises the control lind D by means of the pulse source 270, and the appropriate binary logic levels are fed to the appropriate contact pins 1 to 30 via the enabled HSS as previously explained. The binary output level resulting from this is then fed back to the central control unit 154 on the line 152 and is compared with the level that should be produced if the logic circuit is not faulty, this level being fed to the cental control unit 154 by the store 422.

The foregoing assumes that the store 406 is storing the test information for the particular type of logic circuit to be tested and identified by the operator on the keyboard 408.

However, if the logic circuit to be tested and identified by the operator by means of the keyboard 408 is not one that contained in the store 406, the programming unit 418 will signify this to the operator by means of channel 426, input/output unit 412, channel 428 and the display unit 424. In such circumstances, therefore, the programming unit will request the operator to use the keyboard 408 to enter the basic test information relating to the testing to be carried out on the logic circuit, and the keyboard enters this information into the programming unit 418 by means of a channel 410, the input/output unit 412, and a channel 422; this information will be in terms of the input and output binary signals to be applied to and produced from the various terminals of the logic circuit without reference to the particular contact pins to which they happen to be connected on the particular circuit board 404 under test. This basic test information is then fed by the programming unit 41 8 to the store 406 by means of channel 444 and is stored in the store 406 so as to be available immediately that particular logic circuit has to be tested at any time in the future. The operator will then enter (by means of the keyboard 408 and the line 410) connection information (corresponding to that entered as described above when the store 406 already knows the logic circuit under test) relating the actual terminals of the logic circuit to the particular contact pins 1 to 30 of the contact plate 402.

In the response to this information, the programming unit 41 8 therefore generates the required test patterns identifying the binary signals to be applied to and to be expected from various contact pins of the plate, and this information is stored in the store 422. The central control unit 154 is then able to carry out the testing as described above.

The system may also be arranged so that, as an alternative to the operator entering into the programming unit 418 the actual test sequences to be carried out on a logic circuit for which information has not previously been stored in the store 406, he simply feeds in information describing the logic circuit under test in the form of basic logic elements (AND, OR, NAND gates and the like). In such a case, information relating to such standard logic elements is fed from the store 406 into the programming unit 418, together with the operator's information, so as to allow the programming unit 418 to build up the test sequences as previously.

The process by which the operator feeds into the system information relating to the testing of a logic circuit for which information is not already stored in the store 406, may be interactive, that is te say, the programming unit 41 8 and the store 406 may be arranged to display (on the display unit 424) information relating to the progress of this process so as to guide the operator during the process.

The system may instead be arranged to that, as an alternative to the store 422 being connected to the central control unit 154, the store 422 can be a removable store such as a magnetic disc or tape. The operator would then operate the keyboard in the manner explained, so as to set up the test sequences in the store 422. However, as this store is not connected to the central unit 154, no direct control takes place. Instead the operator is able to remove the record medium bearing the stored test sequences from the store 422, and then take it to a suitable drive unit associated with the central control unit 154 as to drive the latter. By this means, test programs can be generated by the programming circuit 418 and transferred to the central control unit 154 and used at some later date. Also the test program set up in the store 422 can be copied and used by several different central control units associated with different apparatus.

Although the foregoing description has referred primarily to the testing of logic circuits, it will be appreciated that this system can also be used to test electrical components such as resistors and capacitors, and the operation would be broadly as described, the store 406 being arranged to pre-store information relating to the input and output signal levels to be applied to and across such components in order to test them for correctness of value.

Claims (2)

1. Apparatus for the automatic testing of electrical and electronic circuitry, comprising: a plurality of contact means mounted in predetermine physical relationship with each other for making respective and simultaneous contact with predetermined terminals of a circuit to be tested; control means operative in response to predetermined test information respective to the circuit to be tested to apply predetermined test signals to selected ones of the predetermined terminals via the respective contact means and to monitor the value of a resultant output signal produced from a selected one of the predetermine terminals via its respective contact means whereby to determine whether the circuit is operating correct!; or not; means for storinq, for each of a plurality of separately identifiable circuits to be tested, test information defining the predetermined terminals of that circuit to which test signals are to be applied and the resultant output signal which should be produced at one or more predetermined terminals of the circuit if it is operating correctly; input means for identifying a particular circuit to be tested and for feeding the said test information relating to that particular circuit out of the storage means if it is stored therein; generating means for generating test information relating to a circuit to be tested for which test information is not stored in the storage means; means for producing connection information correlating the particular predetermined terminals of that circuit with the particular contact means to which those terminals are temporarily connected; programming means responsive to the test information whether from the storage means or the generating means and to the connection information so as to render the control means operative accordingly; and means of feeding into the storage means the test information produced by the generating means and identifying it therein as relating to one particular circuit so as to enable it to be read out when that circuit is next to be tested.

2. A method of automatic testing of electrical and electronic circuitry, comprising the steps of; mounting in predetermined physical relationship with each other a plurality of contact means for making respective and simultaneous contact with predetermined terminals of a circuit to be tested; storing, for each of a plurality of separately identifiable circuits to be tested, test information defining the predetermined terminals of that circuit to which test signals are to be applied and the resultant output signal which should be produced at one or more predetermined terminals of the circuit if it is operating correctly; identifying a particular circuit to be tested and automatically reading out the said test information relating to that particular circuit from the storage means if it is stored; manually generating test information relating to a circuit to be tested for which test information is not found to be stored; producing connection information correlating the particular predetermined terminals of that circuit with the corresponding ones of the said contact means; responding to the read out or the generated test information and to the connection information to apply predetermined test signals to selected ones of the predetermined terminals via the respective contact means and monitoring the value of a resultant output signal produced from a selected one of the predetermined terminals via its respective contact means whereby to determine whether the circuit is operating correctly or not; and storing the generated test information and identifying it as relating to one particular circuit so as to enable it to be read out when that circuit is next to be tested.

2. A method of automatic testing of electrical and electronic circuitry, comprising the steps of: mounting in predetermined physical relatiohship with each other a plurality of contact means for making respective and simultaneous contact with predetermined terminals of a circuit to be tested; storing, for each of a plurality of separately identifiable circuits to be tested, test information defining the predetermined terminals of that circuit to which test signals are to be applied and the resultant output signal which should be produced at one or more predetermined terminals of the circuit if it is operating correctly; identifying a particular circuit to be tested and reading out the said test information relating to that particular circuit storage means if it is found to be stored; generating test information relating to a circuit to be tested for which test information is not found to be stored; producing connection information correlating the particular predetermined terminals of that circuit with the corresponding ones of the said contact means; responding to the accessed or the generated test information and to the connection information to apply predetermined test signals to selected ones of the predetermined terminals via the respective contact means and monitoring the value of a resultant output signal produced from a selected one of the predetermined terminals via its respective contact means whereby to determine whether the circuit is operating correctly or not; and stowing the generated test information and identifying it as relating to one particular circuit so as to enable it to be read out when that circuit is next to be tested.

3. Apparatus for the automatic testing of electrical and electronic circuitry according to claim 1, and substantially as described with reference to the accompanying drawings.

4. A method of automatically testing electrical and electronic circuitry according to claim 2, and substantially as described with reference to the accompanying drawings.

1. Apparatus for the automatic testing of electrical and electronic circuitry, comprising: a plurality of contact means mounted in predetermined physical relationship with each other for making respective and simultaneous contact with predetermined terminals of a circuit to be tested; control means operative in response to predetermined test information respective to the circuit to be tested to apply predetermined test signals to selected ones of the predetermined terminals via the respective contact means and to monitor the value of a resultant output signal produced from a selected one or more of the predetermined terminals via its respective contact means whereby to determine whether the circuit is operating correctly or not; storage means for storing, for each of a plurality of separately identifiable circuits to be tested, test information defining the predetermined terminals of that circuit to which test signals are to be applied and the resultant output signal which should be produced at one or more predetermined terminals of the circuit if it is operating correctly; manually operable input means for identifying a particular circuit to be tested and for causing the said test information relating to that particular circuit to be fed automatically out of the storage means if it is stored therein; manually operable generating means for generating test information relating to a circuit to be tested for which test information is not stored in the storage means; means for producing connection information correlating the particular predetermined terminals of that circuit with the particular contact means to which those terminals are temporarily connected; programming means responsive to the test information whether from the storage means or the generating means and to the connection information so as to render the control means operative accordingly; and means for feeding into the storage means the test information produced by the generating means and identifying it therein as relating to one particular circuit so as to enable it to be read out when that circuit is next to be tested.