Electronic audio signalling device for telephones

• US 4,214,131 A
• Filed: 12/18/1978
• Issued: 07/22/1980
• Est. Priority Date: 12/18/1978
• Status: Expired

• Current Assignee: Floyd Bell Associates Incorporated
• Original Assignee: Floyd Bell Associates Incorporated
• Inventors: Bush, Terry D., Denen, D. Joseph
• Primary Examiner(s): Fears, Terrell W.
• Assistant Examiner(s): Popek, Joseph A.
• Application Number:
  US05/970,633
• Time in Patent Office: 582 Days
• Field of Search: 179/84 R, 179/84 J, 179/110 A, 181/148, 181/153, 181/156, 181/185, 340/384 E
• US Class Current: 379/395.01
• CPC Class Codes: H04M 19/04 the ringing-current being generated at the substations

Abstract

A signalling device to be substituted for the usual electromechanical ringer of a telephone, either as a replacement for that ringer in existing telephone instruments or as a part of the original manufactured instrument. It includes solid-state circuitry for eliminating noise pulses and an electronic oscillator circuit which will operate effectively on a minimum current supply along with a mechanical arrangement of components to obtain a compact unit with a folded horn or Helmholtz resonator type acoustical loading system and adjustable volume control.

Claims

1. A signalling device for telephones or the like comprising a housing, a printed circuit board mounted within the housing and carrying solid state circuit components in a circuit, a piezoelectric actuated flexible diaphragm also mounted within the housing in spaced relationship to said circuit board, said flexible diaphragm carrying a piezoelectric element connected in the circuit, said circuit including:

a set of leads adapted to be connected to the telephone voltage supply line for receiving signalling voltage therefrom;

a square wave oscillator audio-signalling circuit connected to said leads and including a square wave driving network with oscillator frequency controlling components connected to a buffer driving network including said piezoelectric element;

a rectifying and voltage-limiting network connected between the leads and the oscillator circuit for receiving, rectifying and limiting the voltage supplied by the telephone voltage supply line to a selected range and applying the resulting output voltage to the oscillator circuit, said rectifying and voltage limiting network including a full wave bridge rectifier which effects full wave rectification of the incoming signal voltage allowing both halves to provide voltage to the oscillator circuit, a voltage dropping element connected with the bridge rectifier to serve as a current limiting element to protect the rectifier, and a voltage clamping element connected to the output of the rectifier and cooperating with said voltage dropping element for suppressing the application of voltages other than proper signalling voltages to the oscillator circuit; and

a disabling network connected between the leads and the oscillator circuit for disabling the oscillator circuit except when proper signalling voltage is supplied through said leads so as to prevent undesired audio outputs in the telephone to which it is applied when voltages other than proper signalling voltages are present on the telephone voltage supply line, said disabling network including signal-attenuating components for preventing application of voltages to the oscillator circuit unless they are in the selected range of proper signalling voltages.

2. A signalling device according to claim 1 in which the voltage dropping element comprises a current limiting resistor connected in series with the input of the bridge rectifier and the voltage clamping element comprises a zener diode, connected in parallel to the output of the bridge rectifier.

3. A signalling device according to claim 1 in which a disconnect zener diode is connected in series with the output of the bridge rectifier.

4. A signalling device according to claim 3 in which the signal attenuating components of the disabling network comprise a resistor connected in series with the disconnect zener to the power supply of the oscillator circuit and a capacitor connected from the power supply of the oscillator circuit to ground, and a resistor connected from ground through the oscillator power supply circuit to said capacitor and resistor.

5. A signalling device according to claim 1 in which the oscillator circuit comprises three linear bipolar transistor integrated circuit stages, a resistor connected in parallel with the first stage and in series with a capacitor which is connected to ground, a resistor connected in parallel with the second stage and in series with a capacitor which is connected to ground and a resistor connected in series between the third stage and the piezoelectric element.

6. A signalling device according to claim 5 in which the housing is tubular and has one end as an open outlet end;

said printed circuit board being on a first disc spaced axially within the open end;

said flexible diaphragm being a second disc mounted within the housing axially outwardly of the first disc to provide a space therebetween and carrying the piezoelectric element in the form of a crystal bonded to the diaphragm, the diaphragm being supported by the housing at its edge, said element being connected in circuit with the components on said board.

7. A signalling device according to claim 6 including:

a rigid baffle disc supported within the housing axially outwardly of the second disc and arranged to permit sound waves hitting the baffle disc to be deflected around its edge toward the outlet end of the housing thereby producing a folded horn accoustical loading characteristic.

8. A signalling device according to claims 6 or 7 including:

an adjustable mechanical volume control carried by the tubular housing adjacent its outlet end and spaced outwardly of said rigid baffle disc and consisting of;

relatively rotatable discs in superimposed relationship which have cooperating openings adapted to provide sound wave passages when in communication and movable relatively to vary the size of or close said passages.

9. A signalling device for telephones or the like comprising a housing, a printed circuit board mounted within the housing and carrying solid state circuit components in a circuit, a piezoelectric actuated flexible diaphragm also mounted within the housing in spaced relationship to said circuit board, said flexible diaphragm carrying a piezoelectric element connected in the circuit, said circuit including:

a set of leads adapted to be connected to the telephone voltage supply line for receiving signalling voltage therefrom;

an oscillator audio-signalling circuit connected to said leads and including said piezoelectric element;

a rectifying and voltage-limiting network connected between the leads and the oscillator circuit for receiving, rectifying and limiting the voltage supplied by the telephone voltage supply line to a selected range and applying the resulting output voltage to the oscillator circuit, said rectifying and voltage limiting network including a full wave bridge rectifier which effects full wave rectification of the incoming signal voltage allowing both halves to provide voltage to the oscillator circuit, a voltage dropping element connected with the bridge rectifier to serve as a current limiting element to protect the rectifier, and a voltage clamping element connected to the output of the rectifier and cooperating with said voltage dropping element for suppressing the application of voltages other than proper signalling voltages to the oscillator circuit; and

a disabling network connected between the leads and the oscillator circuit for disabling the oscillator circuit except when proper signalling voltage is supplied through said leads so as to prevent undesired audio outputs in the telephone to which it is applied when voltages other than proper signalling voltages are present on the telephone voltage supply line, said disabling network including signal-attenuating components for preventing application of voltages to the oscillator circuit unless they are in the selected range of proper signalling voltages.