GB2059653A - Pushbutton set - Google Patents

Abstract

In a telephone instrument in which the wanted number digit sending is effected without moving parts, optical techniques are used. The instrument has a coordinate array of digit positions with light beams from a source (5) aimed along the rows and columns of the array. At the other ends of the rows and columns are light detectors (8), coupled to an electronic circuit. To send a digit the user puts his finger into the array at the position for the digit to be sent, which interrupts two of the beams. The digit positions are defined by holes in a cover or by upstanding walls in a block of insulating material. <IMAGE>

Description

SPECIFICATION Pushbutton set This invention relates to signal transmitting arrangement of the "multi-switch" variety, i.e.

one in which a number of different signals have to be transmitted, under the control of manual operation.

An example of the signal transmitting arrangements to which the present invention is applicable is a telephone subscriber's instrument. Contemporary instruments of this type use either rotary dials or push-button sets, which are mechanical devices with moving parts. In order to reduce costs it is desirable, as far as possible to eliminate such moving parts. Hence it is an object of the invention to provide a signal transmitting arrangement with as few moving parts as possible.

According to the present invention there is provided a signal transmitting arrangement which has a co-ordinate matrix of operative positions each of which corresponds to a signal to be sent from the arrangement, first and second sets of light channels extending respectively parallel to the rows and columns of the matrix, a light source means for projecting light beams along the channels from one end of each of the channels, and light detectors at the other ends of the channels, wherein to send a digital value or other signal the user places a finger at the operative position for that signal so that that finger interrupts two of the light beams, and wherein circuit means is provided which is coupled to the detectors and which in response to the interruptions causes the transmission of signals appropriate to that digital value or other signal.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a cross-section of a telephone digit sending arrangement embodying the invention.

Figure 2 is a plan view of the arrangement of Fig. 1, shown with the cover plate removed.

Figure 3 is a top plan view and Fig. 4 a perspective view of another telephone subscriber's digit sender including the invention.

We now refer to Figs. 1 and 2, in which 1 is the cover of a telephone subscriber's instrument, having finger holes 2 arranged in a coordinate matrix for the digits 1 to 9 and 0 and two additional codes. Mounted below the array of holes there is an opaque tray 3, whose side walls have holes such as 4 each aligned with either a row or a column of the matrix: The designations appropriate to each hole are printed on the upper surface of the tray 3 and are thus clearly visible to the user.

There is a light source 5, such as a pea bulb, from which light is deflected along the rows and columns by reflecting surfaces indicated at 6, 7. These reflecting surfaces can be replaced by light guiding arrangements such as plastics rods or optical fibres to avoid risk of dust contamination of the light paths associated with the reflecting surfaces. At the opposite end of each of the rows and columns there is a light detector 8; in the present case photo-diodes are used, although photo-transistors can also be used.

When the arrangement is to be used the light source is enabled, e.g. in response to the subscriber off-hooking, so that light beams are projected along the rows and columns of the matrix. Hence at each row-column intersection, there are two light paths crossing, as indicated, for example at 9. To send a digit, the subscriber inserts his finger into the hole in the cover which corresponds to the digit or other signal to be sent, as shown at 10. This interrupts two of the beams so that the light is cut off from two of the light detectors, one for a row of the matrix and the other for a column thereof.

Electronic circuitry crossmounted with the light detectors determines from the two light detectors from which the light has been cut off the identity of the digit or other signal to be sent, and then sends it, using either "Strowger-type" pulsing or multi-frequency codes. This circuitry is analogous to that used for sending digits under control of a coordinate array of push-buttons.

To minimise difficulties due to the collection of dust in the arrangement, the cover over the light beam array can be made to flap up for easy cleaning. Alternatively a thin sheet of rubber or a rubber-like material could be glued to the underside of the case top, in which case the designations are printed on the thin sheet so as to be visible to the user.

In such case the finger insertion causes the sheet to be pushed downwards as the finger enters the hole.

The arrangement shown in Figs. 3 and 4 is another approach to solving problems due to the accummulation of dirt. In this, the digit array is made from a moulded block 20 having channels defined by two walls 21, 22, with small blocks such as 23 in the channels to define the digit positions. The blocks could also each be integral with the two adjacent walls to define a matrix of walls. The blocks and walls have holes as shown at 25 and 26 to define light paths. These light paths are indicated at 27, 28 in Fig. 3.

As can be seen from Fig. 3, the light detectors 29, 30 are enclosed within the moulded block 20. The light source (not shown) is also enclosed in the moulded block 20, with light guiding means to couple it to the ends of the rows and columns.

Operation is the same as in the arrangement of Figs. 1 and 2, i.e. the user puts his finger into the paths of a pair of intersecting light beams, with detection and sending as already described.

The moulding arrangements are such that the edges which appear to be sharp in Fig. 3 are in fact moulded to have generous radii. To clean the "key pad". it is wiped from above, in which case the gaps indicated at 31 facilitate the removal of any accumulated dirt.

Claims (9)

1. A signal transmitting arrangement which has a co-ordinate matrix of operative positions each of which corresponds to a signal to be sent from the arrangement, first and second sets of light channels extending respectively parallel to the rows and columns of the matrix, a light source means for projecting light beams along the channels from one end of each of the channels, and light detectors at the other ends of the channels, wherein to send a digital value or other signal the user places a finger at the operative position for that signal so that that finger interrupts two of the light beams, and wherein circuit means is provided which is coupled to the detectors and which in response to the interruptions cause the transmission of signals appropriate to that digital value or other signal.

2. An arrangement as claimed in claim 1, and wherein the operative positions are defined by holes in a cover plate behind which the light source means and the light detectors are located.

3. An arrangement as claimed in claim 1 or 2, and wherein the light source means is a lamp plus a set of reflecting surfaces which reflect light from the lamp along one of the rows or one of the columns.

4. An arrangment as claimed in claim 1 or 2, and wherein the light source beam is a lamp with which there are associated light guiding means to guide light from the lamp to one end of each of the rows and columns of the matrix.

5. A telephone subscriber's instrument which has a co-ordinate matrix of holes in its outer cover each of which corresponds to a digital value or other signal to be sent from the instrument, first and second sets of light channels extending respectively parallel to the rows and columns of the matrix, light source means for projecting light beams along said channels from one end of each such channel when a wanted number or signal is to be sent, and light detectors at the other end of each of said channels, wherein to send a digit of a wanted number or other signal the user inserts a finger into the hole for that digit or signal so that the finger interrupts two of the light beams, one for a row and one for a column of the matrix, and wherein circuit means is provided which is coupled to the detectors and which in response to the interruptions causes the transmission of signals appropriate to that digit or other signal.

6. An arrangement as claimed in claim 2, 3 or 4 or an instrument as claimed on claim 5, and wherein the portion of the cover which overlies the light paths can be hinged upwards to facilitate cleaning.

7. An arrangement as claimed in claim 2, 3 or 4 or an instrument as claimed in claim 5, and which includes a thin sheet of rubber or of a rubber-like material secured to the inner face of the cover in the region of the operative positions or of the holes.

8. An arrangement as claimed in claim 1, which includes a moulded block of a plastics material having upstanding portions to define a matrix of said operative positions, said upstanding portions having holes therein to define the light channels.

9. A signal transmitting arrangement, substantially as described with reference to Figs.

1 and 2 or Figs. 3 and 4 of the accompanying drawings.