AU688572B2 - Network service status indicators - Google Patents

Description

P/0101O1 28/5/91 Rogulatlon 342

AUSTRALIA

Patent&AcLLM9

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: 9

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"NETWORK SERVICE STATUS INDICATORS" The following statement is a full description of this invention, including the best method of performing it known to us:rO 0 3 0 3 U*2 T

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This invention relates to telephone subsets and in particular to telephone subsets connected to an exchange having exchanged based facilities.

Exchange based facilities can be accessed by the user of a telephone by dialling certain codes usually in dual tone multi frequency signals (dtmf). The facilities may be of a type that can be activated by one code and deactivated by the user sending another code to the exchange. The user may wish to know if the facility is activated or deactivated, particularly with facilities such as divert where call may be missed if the facility is active unbeknown to the user.

Another facility is an exchange based message wait, where a message from another party may be stored in the exchange. The user needs to be aware of the message and a positive indication may be useful. To date, this has been done by changing the type of dialtone received by the user or sending a special message to the telephone similar to the called-identification signal.

Some telephones are provided with a liquid crystal display (LCD) which may indicate when a facility is activated, but such displays do not easily attract the attention of the user and require close inspection to determine which facilities are activated.

LCD are difficult to read in low light and have a narrow field of view, To provide a subset with an indicator means having an adequate light or :O sound emission, a battery powered arrangement would be required because, to provide a more advantageous line powered device, a level of ON-HOOK line current would be required which would exceed the maximum ON-HOOK line current, typically 50 pA, permitted by most telecommunication authorities.

It is an object of the present invention to provide a line powered arrangement I.:2 which provides a highly visual or audible indication of an activated exchange based facility.

According to the invention, there is provided a telephone status indication arrangement to indicate the status of one or more exchange based services available to the telephone connected to the exchange via an exchange line, said arrangement including at least one light or audible sound emitting means driven by a control means powered by line bleed current when said telephone is in an ON-HOOK mode, wherein said control means turns said emitting means on and off with a duty cycle 3 such that the average current supplied via the line is less than a predetermined average line bleed current, current to turn on the said emitting means being substantially greater than the predetermined average line bleed current.

In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the accompanying drawings, in which: Figure 1 shows a telephone circuit including a first embodiment of the status indication arrangement of the present invention.

Figure 2 shows a telephone circuit including a second embodiment of the status indication arrangement of the present invention.

Figure 3 shows a block diagram of a third embodiment of the present invention.

Figure 4 shows a timing diagram for a pair of oscillators and their combined output.

Referring to Figure 1 there is shown an embodiment of the arrangement for providing a pulsed current to an LED, while maintaining the line bleed current below the permitted threshold.

The telephone circuit would normally contain a bridge rectifier providing a DC output (typically 48V when the phone is ON HOOK). The bleed circuit includes a first 2. resistor R1 IM 0 whose value is selected to ensure that the bleed current i remains below the permitted threshold. Resistor R1 is in series with zener diode D1, which in turn feeds into transistor TR1, whose emitter collector path is in series with a divider formed by resistors R2 and R3, across the 48V line voltage. The emitter base path of transistor TR1 is connected to diode D2 which feeds into capacitor C1 which is connected to the telephone circuit ground, A second zener diode D3, which may be external to the telephone speech and memory circuits, is connected across capacitor C1 (typically 1000 to maintain a constant voltage to supply the telephones memory when the phone is ON HOOK.

A series of gates G1, G2, G3 and G4 are arranged to provide control of the pulse current from capacitor Cl to LEDI1 via transistor TR2 and resistor R6. The S gates G1, G2, G3 and G4 are Schmitt trigger NAND gates which have a hysteresis characteristic due to the fact that, for an increasing signal voltage, the voltage to trigger the gate is higher than the voltage to trigger the gate when the signal voltage is decreasing. Gate G3 is arranged to operate as a relaxation oscillator having paths provided by resistor R4, and by diode D4 in series with resistor R5. Capacitor C2 also forms part of the timing circuit of the oscillator.

NAND gate has following truth table A B I C 0 0 I 1 0 1 I 1 1 0 1 1 1 I 0 where A and B are inputs and C is the output.

If A or B is held at 1 the output C 1.

1 5 If either A or B is held at 1 the gate acts as an invertor of the other input.

In the oscillator shown in the embodiment, assume that the output of gate G2 is high and that capacitor C2 is uncharged. Therefore the output of gate G3 is high and capacitor C2 charges through resistor R4. When capacitor C2 reaches the upper trigger level of gate G3, the output of G3 changes state and the capacitor discharges through diode D4 and resistor R5 in parallel with resistor R4. Resistor R4 is chosen to be rcsistor R5 in this case, When the discharging capacitor C2 reaches the lower trigger level of gate G3, the output of gate G3 changes state and the proces- is repeated producing an oscillation.

If the output of gate G2 is low, the oulput of gate G3 is forced high and no oscillation can occur because when one input is low, the output of the NAND gate is high regardless of the other input state.

While the gate circuits are shown as NAND gates, other control circuits capable of performing the same function may be used.

Zener diode D1 a 12V zener ensures that transistor TR1 is OFF when the line voltage drops below a predetermined threshold, 20V as in the case of a parallel telephone being taken OFF-HOOK or the line being severed. This ensures that the junction of resistors R2 and R3 is at 0V and this causes gates G1 and G2 to hold the oscillator formed by gate G3 OFF. As a consequence, transistor TR2 is held OFF and the LED 1 is not energized. This is important where capacitor C1 serves the dual function of providing power for the LED and for the telephone's memory.

Diode D2 prevents capacitor C1 discharging via the base collector path of transistor TR1.

The main flashing/timing circuit is the first relaxation oscillator formed by Schmitt trigger NAND gate G3 and resistors R4 and R5, diode D4, and capacitor C2.

The oscillator is controlled by the state of the output of gate G2. If this output is high, the oscillator is functioning, if it is low the oscillator is not.. The gate G2 is an inverter to ensure that when the output of gate G3 is high (oscillator not operating) the LED 1 is off as the base of transistor TR2 is held low. The current flowing through LED 1 is controlled by resistor R6 and transistor TR2.

Under normal operating conditions transistor TR1 is on (saturated) as is zener diode D1. The resistors R2 (typically 47K) and R3 (typically 470K) ensure that the gate G1 input is correctly biased i.e. high for normal operation.

The telephone speech circuit may have an internal limiting diode D3 (typically 6V) but this may also be provided externally. This limits the voltage to which the bleed current can charge capacitor C1.

I The other input to gate G1 is from the dialler or microprocessor (controller) (not shown). This input, when taken high (as would be the case if a network service key were pressed to activate the service) will cause the oscillator gate G3 to start provided that the other input to gate G1 is high (as it would be if the line is properly connected and no parallel telephone is active).

If the network service is deactivated, the microprocessor would set the input of gate G1 low and the oscillator would stop and the LED 1 would be out.

The microprocessor provides the dialling and other control functions of the telephone.

30; When a particular exchange based service is de-activated the jup output is low and the oscillator is stopped.

When the user activates the exchange based service by pressing the 6 appropriate button on the telephone, the /p dials the appropriate code to the exchange and also sets the input to gate G1 high thereby starting the oscillator G3.

Preferably the gates G1, G2, G3, G4 are part of a CMOS gate package for low current consumption.

The current drawn from the line via this arrangement is substantially constant and limited to below the permissible threshold because the bleed resistor R1 is large and small changes in voltage of capacitor C1 will not greatly affec the current drawn from the line.

Referring to Figure 2, the arrangement shown is the same as that described in relation to Figure 1 except that a second retaxation oscillator, comprising an arrangement of a CMOS gate G5, resistor R7 and capacitor C3, is operatively interposed between the flashing/timing circuit formed by the NAND gate G3, resistors R4, R6, and capacitor C2. The said flashing/timing circuit switches the second 1 5 relation oscillator on and off producing pulses of audio signai which are invented by gate G6 and applied to the base element of transistor TR2 to drive transducer T which produces and audible tone. Preferably, transducer T is a current driven dynamic transducer.

Referring to Figure 3, power for the circuit is derived from the telephone line via the bleed resistor R1 as described in relation to Figure 1.

Control (enable) lines EN1 and EN2 connect to the microprocessor.

If LED 1 is to be active, line EN1 is asserted. If the LED 2 is to be active, line EN2 is asserted. If both LED's are to be active, both lines EN1 and EN2 are asserted by the microprocessor.

The control circuit determines whether the oscillators are to be on and which LED is to be on.

Control circuit 3 is responsive to inputs EN1 and EN2 to turn on both oscillators 4 and 5 if either or both inputs EN1 and EN2 are activated. Thus the output of OR gate G7 is a combination of the outputs of the oscillators 4 and 30: If only one of the inputs, EN1, is activated then control circuit 3 instructs a Driver Circuit 6 to cause the corresponding LED 1 to be driven by the output of OR gate G7 so that LED 1 flashes at the rate of the combined outputs of oscillators 4 and Similarly if only input EN2 is activated, LED 2 is driven at the combined rate.

However, if both inputs EN1 and EN2 are activated, control circuit 3 instructs the driver circuit 6 to apply the output of oscillator 4 to drive LED 1, and to apply the output of oscillator 5 to drive LED2. Thus the combined rate of LEDs 1 and 2 is the same as the rate when only one LED is driven.

When both inputs EN1 and EN2 are de-activated, control circuit 3 causes both oscillators 4 and 5 to be switched off.

The LED driver circuit 6 provides the interface between the LED's and the low current CMOS control circuit.

The oscillator circuits 5) could be identical except that they would generate signals with the appropriate phase relationship, the pulses being interleaved as shown in Figure 4.

The signals could also be generated using a single oscillator and gating circuits.

Referring to Figure 4, in an embodiment of the invention, an average line current less than 50 pA can be drawn from the line if t 25 mill;econds T 1 second, and i. 10 microamps i, 50 pA and ip milliamp, where i, is the average line current, i, is the pulse current for the LED and i, is the steady state drain for the telephone memory.

The arrangement shown in Figure 4 may be adapted so that sound transducers could substitute the LEDs 1 and 2. In this case two audio oscillators would be operatively coupled to drive circuit 6 to provide the acoustic energy for the transducers (not shown) coupled to the driver.

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Claims (9)

1. 2. An arrangement as claimed in claim 1, wherein the control means draws off a substantially smoothed bleed current which is less than the predetermined line bleed current to charge an electrical energy storage device, said control means controlling the release of energy frorn said storage device to energize said emitting means according to said duty cycle.
2. 3. An arrangement as claimed in claim 1 or 2, including a bleed resistor in series with a storage capacitor to draw a current less than a predetermined threshold current from the exchange line, a light emitting diode in series with a switch means supplied from the storage capacitor, said control means operating the switch with a .i duty cycle so as to produce a pulse current whose average value is less than said threshold current and wherein the pulse current is sufficient to drive the light emitting diode.
3. 4. An arrangement as claimed in claim 1 or 2, including a bleed resistor in series i.J: with a storage capacitor to draw a current less than a predetermined threshold current from the exchange line, a transducer means in series with a switch means and an audio oscillator means whose output is coupled to said transducer via a switching path of said switch, said switch and said oscillator means being supplied from the storage capacitor and control means to operate said switch and said oscillator means with a duty cycle so as to produce a pulse current whose average value is less than *e said threshold current and wherein the said pulse current is sufficient to transduce said oscillator means output in said transducer. i 9 An arrangement as claimed in claim 3, wherein an inverter means is operatively interposed between the output of the oscillator means and the switch.
4. 6. An arrangement as claimed in claim 3, 4 or 5, wherein the control means includes a relaxation oscillator powered from the storage capacitor.
5. 7. An arrangement as claimed in claim 6 wherein the telephone includes processor means to generate a status signal indicating whether or not a network service is activated, the status signal enabling or inhibiting the oscillator depending on whether or not the network service is activated or not respectively.
6. 8. An arrangement as claimed in any one the preceding claims including line voltage sensitive means to ensure that the emitting means is held off if the line voltage falls below a predetermined voltage.
7. 9. An arrangement as claimed in any one of claims 2 to 8 wherein the storage capacitor is shunted by a zener diode.
8. 10. An arrangement as claimed in claim 9 wherein the storage capacitor is used to maintain the telephone's memory when the telephone is in an ON-HOOK mode.
9. 11. A telephone status indicator substantially as herein described with reference to Figures 1 4 of the accompanying drawings. DATED THIS TWENTY-FIRST DAY OF SEPTEMBER 1995 ALCATEL AUSTRALIA LIMITED 000 005 363) S...i ABSTRACT A high visibility telephone status indicator arrangement to indicate the status of one or more network services available to the telephone via the telephone network, includes a light emitting device driven by a line powered control means, wherein the control means turns the light emitting device on and off with a duty cycle such that the average current supplied via the line is less than a permitted average line bleed current, the current to turn on the light emitting device being substantially greater than the permitted average line bleed current. *too *00000 0 S 6 o 0 a 5*55 r