GB1559846A - Telecommunication push-button signalling device - Google Patents

Description

(54) TELECOMMUNICATION PUSH-BUTTON SIGNALLING DEVICE (71) We, THE PLESSEY COMPANY LIMITED, a British Company of 2/60 Vicarage Lane, Ilford, Essex, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to push-button signalling devices suitable for signalling from telecommunication stations.

It is known to provide a telecommunication station, for example, a telephone instrument, with a push-button device by which the digits of a wanted number may be signalled to an exchange. Such devices generally have ten push-buttons, one for each of the digits 0-9, and may have further push-buttons for other purposes. Operation of a push-button causes a distinctive electrical code to be applied to a line connecting the station to the exchange. Each push-button operates a number of contacts dependent on the complexity of the code.

The resulting multiplicity of contacts may give rise to difficulties when a device is in service.

According to the invention there is provided a telecommunication push-button signalling device, capable of signalling a number of digits as a distinctive combination of tone frequencies selected from a range of tone frequencies, which includes: (i) a tone frequency generator capable of generating simultaneously each tone frequency of a range of tone frequencies; (ii) a coincidence gate in respect of each tone frequency, each gate being supplied with the relevant tone frequency by the generator, (iii) a pushbutton corresponding to each of the digits each button operating a single associated make contact;; (iv) in respect of each push-button, a multiple connection from the single associated make contact to each of the gates appropriate to tone frequencies representing a code combination of tone frequencies distinctive of the digit to which the relevant push-button corresponds.

An embodiment of the invention installed with a telephone instrument will now be described. Reference will be made to a schematic diagram shown in the drawing accompanying the provisional specification.

A line L, which connects the telephone instrument with an exchange (not shown) is terminated at the instrument at the cradle switch C. When the receiver is lifted off the cradle switch, power from the line L is delivered, over contact cl (closed), to a tone frequency generator G, and to each of a number of push-buttons of which one is shown at P. The contact c2 of the cradle switch closes to connect the outlet of a mixer M to the line L by way of a make contact p. By means of a mechanical linkage (not shown), the make contact p closes each time a push button P is operated.

The tone frequency generator G responds to the application of power to generate each frequency of a range of tone frequencies.

Any suitable number and range of frequencies may be used. As shown the generator G delivers four tones in a relatively low frequency band 1. and four more tones in a relatively high frequency ;band h. A signalling code is used in which each of the digits is represented by a distinctive combination of two tones, one selected from each band.

A push-button P is provided in respect of each of the digits. The push-button P in the drawing is typical. Circuitry associated with and individual to a push-button P is shown in the drawing between the broken lines y, z. The push-button P represents a particular digit. This digit has a distinctive code signal comprising a dis tinctive combination of two tone frequencies, one in the low band and one in the high band. A two-input AND gate is provided in respect of each tone frequency of the combination. The relatively lower frequency is applied to the gate gi, and the relatively higher frequency to the gate gh.

At its simplest, a direct connection from the push-button P is multipled over the gates gi, gh. With this arrangement, the gates gl, gh are enabled when the pushbutton P is operated, and the tones applied to these gates are delivered to a mixer M and thence to the line L over the contact p (closed).

in the simple arrangement described in the previous paragraph the duration of the signal delivered to the line L is dependent on the length of time for which the pushbutton P is operated. To provide signals of constant duration, the multiple connection from the push button P to the gates gi, gk includes a delay device D and a toggle circuit comprising an AND gate ga and a bistable device B. An outlet to a common OR gate gb is also provided. The outlet of the gate ssb is connected to a common timer circuit T, whose output is applied to the gate ga. Conveniently the timer circuit is a monostable device, as shown, which restores itself after timing a desired interval. The desired interval is slightly longer than the desired duration of a coded signal on the line L.

When a push-button P is operated, the relevant delay device D and the common timer circuit T both respond. The timer T applies an input signal to the gates ga associated with each of the push-buttons P. A delay device D delivers an output signal after a delay sufficient to ensure that the timer T has responded. The output signal from the said relevant delay device D, therefore, opens the relevant gate ga which operates the bistable device B and opens the gates gi, gh, thereby delivering to the mixer M the tone frequencies appropriate to the digit to which the operated pushzbutton relates. The gates gi, gh remain open until the bistable device B is restored. This occurs when the timer T restores itself.The gates gl, gh are therefore open for a time equal to the interval timed by the timer T less the delay timed by the delay device D. By choosing suitable values for the interval and the delay, the gates gl, gh are held open for a period equal to the desired duration of a signal on the line L. This period is achieved independently of the time for which the pushbutton P is closed. The output from the delay device D terminates when the push button P is released. The contact p may be dispensed with.

The device is susceptible to many variations, for example, any number of pushbuttons may be provided, each with its own distinctive code. The code shown is a two-out-of-eight code, but any other suitable code may be used, for instance a threeout-of-nine code. In this event, three gates would be provided instead of the pair of gates gi, gh. The toggle action of the gate ,, and the bistable device B may, if desired, be performed by an RS toggle circuit.

The device may be realised by using discrete components. Alternatively, some or all of the following may ;be incorporated in one or more integrated circuit chips : - the generator G, the delay device D, the gate ga and the bistable device B, the gates gS, gh, the gates gb; the timer circuit T and the mixer M.

The generator 0, delay device D, timer circuit T and mixer M may be of any suitable construction.

WHAT WE CLAIM IS: 1. A telecommunication push-button signalling device, capable of signalling a number of digits as a distinctive combination of tone frequencies selected from a range of tone frequencies which includes: (i) a tone frequency generator capable of generating simuItaneously each tone frequency of a range of tone frequencies; (ii) a coincidence gate in respect of each tone frequency, each gate being supplied with the relevant tone frequency ;by the generator; (iii) a push-button corresponding to each of the digits each button operating a single associated make contact; ; (iv) in respect of each push-button, a multiple connection from the single associated make contact to each of the gates appropriate to tone frequencies representing a code combination of tone frequencies distinctive of the digit to which the relevant push-button corresponds.

2. A telecommunication push-button sig

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. tinctive combination of two tone frequencies, one in the low band and one in the high band. A two-input AND gate is provided in respect of each tone frequency of the combination. The relatively lower frequency is applied to the gate gi, and the relatively higher frequency to the gate gh. At its simplest, a direct connection from the push-button P is multipled over the gates gi, gh. With this arrangement, the gates gl, gh are enabled when the pushbutton P is operated, and the tones applied to these gates are delivered to a mixer M and thence to the line L over the contact p (closed). in the simple arrangement described in the previous paragraph the duration of the signal delivered to the line L is dependent on the length of time for which the pushbutton P is operated. To provide signals of constant duration, the multiple connection from the push button P to the gates gi, gk includes a delay device D and a toggle circuit comprising an AND gate ga and a bistable device B. An outlet to a common OR gate gb is also provided. The outlet of the gate ssb is connected to a common timer circuit T, whose output is applied to the gate ga. Conveniently the timer circuit is a monostable device, as shown, which restores itself after timing a desired interval. The desired interval is slightly longer than the desired duration of a coded signal on the line L. When a push-button P is operated, the relevant delay device D and the common timer circuit T both respond. The timer T applies an input signal to the gates ga associated with each of the push-buttons P. A delay device D delivers an output signal after a delay sufficient to ensure that the timer T has responded. The output signal from the said relevant delay device D, therefore, opens the relevant gate ga which operates the bistable device B and opens the gates gi, gh, thereby delivering to the mixer M the tone frequencies appropriate to the digit to which the operated pushzbutton relates. The gates gi, gh remain open until the bistable device B is restored. This occurs when the timer T restores itself.The gates gl, gh are therefore open for a time equal to the interval timed by the timer T less the delay timed by the delay device D. By choosing suitable values for the interval and the delay, the gates gl, gh are held open for a period equal to the desired duration of a signal on the line L. This period is achieved independently of the time for which the pushbutton P is closed. The output from the delay device D terminates when the push button P is released. The contact p may be dispensed with. The device is susceptible to many variations, for example, any number of pushbuttons may be provided, each with its own distinctive code. The code shown is a two-out-of-eight code, but any other suitable code may be used, for instance a threeout-of-nine code. In this event, three gates would be provided instead of the pair of gates gi, gh. The toggle action of the gate ,, and the bistable device B may, if desired, be performed by an RS toggle circuit. The device may be realised by using discrete components. Alternatively, some or all of the following may ;be incorporated in one or more integrated circuit chips : - the generator G, the delay device D, the gate ga and the bistable device B, the gates gS, gh, the gates gb; the timer circuit T and the mixer M. The generator 0, delay device D, timer circuit T and mixer M may be of any suitable construction. WHAT WE CLAIM IS:

1. A telecommunication push-button signalling device, capable of signalling a number of digits as a distinctive combination of tone frequencies selected from a range of tone frequencies which includes: (i) a tone frequency generator capable of generating simuItaneously each tone frequency of a range of tone frequencies; (ii) a coincidence gate in respect of each tone frequency, each gate being supplied with the relevant tone frequency ;by the generator; (iii) a push-button corresponding to each of the digits each button operating a single associated make contact;; (iv) in respect of each push-button, a multiple connection from the single associated make contact to each of the gates appropriate to tone frequencies representing a code combination of tone frequencies distinctive of the digit to which the relevant push-button corresponds.

2. A telecommunication push-button sig

nalling device as claimed in claim 1 including a timer for controlling the period of time that the combination of tone frequencies are generated.

3. A telecommunication push-button signalling device as claimed in claim 2 including a delay for delaying generation of the combination of tone frequencies until after operation of the timer.

4. A telecommunication push-button signalling device as claimed in any one of claims 1, 2 or 3 in which some or all of the action circuit components are constituted by an integrated circuit.

5. A telecommunication push-button signalling device capable of signalling a number of digits as a distinctive combination of tone frequencies selected from a range of tone frequencies substantially as described with reference to the drawing accompanying the provisional specification.