Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04M—TELEPHONIC COMMUNICATION
  • H04M1/00—Substation equipment, e.g. for use by subscribers
  • H04M1/82—Line monitoring circuits for call progress or status discrimination

Definitions

• the subject invention relates to a new and improved switch particularly adapted for use with a telephone. More particularly, an electro-optical switch is disclosed which is operable in any ambient light conditions.
• switch means for activating the circuitry when a user wishes to place a call.
• the most common form of switch includes a spring biased mechanical contact.
• a pair of spring biased members are located in the cradle.
• the handset is lifted from the cradle permitting the spring biased members to rise, activating the telephone circuit.
• the handset is replaced in cradle, depressing the members, thereby breaking the circuit.
• Nonmechanical switches offer the additional advantage of having no moving parts which could wear out.
• Nonmechanical switching device includes the use of photodetectors.
• the simplest type of photodetector switch is one which is actuated by the reception of the ambient light in the room.
• the photodetector In use, the photodetector is mounted so that it is shielded from ambient light when the handset rests on the cradle of the telephone.
• the photodetector When the user wishes to make a call and picks up the handset, the photodetector is exposed to the light in the room and generates a current which can be used to actuate the telephone circuit.
• this type of system is highly unreliable because it is dependent upon ambient light conditions for actuation. Stated differently, if the light present in the room is not enough to cause a trigger voltage to be generated, the phone circuit will not be actuated.
• An improvement over the latter photodetector configuration includes the provision of a photoemitter. More particularly, a photoemitter can be located in a manner to continually actuate the photodetector when the handset rests in the telephone cradle. This result can be achieved by mounting the photodetector and emitter in alignment, on opposed elements of the telephone. By this arrangement light generated by the emitter is transmitted to and received by the detector.
• the subject invention provides a switch means particularly adapted for use with a telephone.
• the switch includes a photoemitter and detector combination which are disposed in a manner such that when the phone is in the aligned, on-hook condition, light generated by the photoemitter is received by the photodetector.
• the photoemitter and detector combination are disposed in a manner such that when the phone is in the aligned, on-hook condition, light generated by the photoemitter is received by the photodetector.
• co bination can be a reflective or trans issive array.
• the subject invention further includes a generator capable of producing an oscillating signal having a frequency on the order of 10,000 kilohertz.
• the output of the generator is supplied to the photoemitter such that high frequency light pulses are generated.
• a logic circuit means is connected to the photodetector as well as to the square wave generator.
• the logic circuit means is configured to produce a first output signal when the inputs from the generator and the photodetector are the same.
• the logic circuit means will produce a second output signal when the inputs received are different.
• both the inputs to the logic circuit means are identical, such that the first signal is produced and can be used to indicate the on-hook condition.
• the photodetector when the handset of the telephone is removed from the cradle, the photodetector will no longer receive the pulsed light from the emitter. Rather, the photodetector will receive whatever ambient light is available in the room. The output of the detector is therefore dependent upon the ambient light conditions. This output is supplied to logic circuit means along with the output from the generator. Since the output from the detector is different from the pulsed signal of the generator, the logic circuit means will produce the second output signal and can be used to actuate the telephone circuitry.
• the logic circuit means includes an "exclusive-or" gate.
• an exclusive-or gate produces a first or low output when the inputs thereto are identical.
• a second or high signal is generated.
• the output produced by the detector is identical to the generator.
• the first, low signal is produced.
• the inputs to the gate are different so that the second, high signal is produced.
• the output from the gate is integrated and compared to a reference voltage in order to generate a signal which can be used to actuate the telephone circuits.
• Figure 1 is a block diagram illustrating the new and improved switch of the subject invention.
• FIG. 2 is a circuit diagram illustrating the component parts of the new and improved switch of the subject invention.
• Figure 3 is a graph illustrating the types of inputs received by the logic circuit means of the switph of the subject invention.
• Switch 10 is a photoelectrical device which is operable in all ambient light conditions.
• Switch 10 is particularly adapted for use as an indicator in a telephone system where data link communications are involved.
• the bouncing of the contacts associated with typical mechanical switches frequently introduce spurious pulses into the communication line which will interfere with data transmission.
• various electro-optical switches were developed to eliminate the mechanical contacts.
• the prior art switches operated effectively only under optimum ambient light conditions.
• the subject switch 10 is operable in any ambient light situation.
• a generator means 20 is provided for producing an oscillating output.
• generator means 20 is configured to output a square wave signal of transitor-transitor logic (TTL) pulses alternating between zero and +5.0 volts.
• TTL transitor-transitor logic
• Generators of this type are well known in the art and need not be further described.
• the output of generator means 20 is supplied to a photoemitter 22.
• Photoemitter 22 is configured to generate light in response to the pulses supplied by the generator means 20. As illustrated in Figure 2, photoemitter 22 is preferably defined by a photodiode. Photoemitter 22 is paired with a compatible photodetector 24 capable of generating an electrical output in response to the reception of light 24.
• the emitter and detector are mounted to the elements of the telephone in a manner such that light generated from the emitter is received by the detector only when the elements are in an aligned position.
• one of the optical elements can be affixed to the base of the telephone while the remaining element is affixed to the handset.
• the optical elements are mounted in a manner such that when the handset is in place in the cradle on the telephone, light generated by the photoemitter 22 is received by the photodetector 26.
• the handset of the telephone is removed from the cradle, such that the optical elements are no longer aligned, light from the emitter is unable to reach and actuate the detector.
• transmissive photoemitter detector system In addition to transmissive systems, various other emitter detector systems are known and used in the prior art. For example, reflective photodiode assemblies are known, which are formed as a single unit, wherein light generated by the emitter is reflected back and received by the integrally associated detector. If the latter
• C ' _ ⁇ ⁇ type of assembly were used in conjunction with the subject invention, it could be mounted, for example, on either the handset or the base of the telephone in a position such that the remaining element of the telephone acts as the reflecting surface when the handset rests in the cradle of the phone.
• the removal of the handset from the cradle breaks the reflecting path such that only ambient light will be received by the detector.
• the scope of the subject invention is not intended to be limited by the type of photoemitter detector assembly used. It is merely necessary to provide an assembly wherein light generated by the photoemitter is only received by the photodetector when the elements, whose movement is to be sensed, are in an aligned position. Therefore, when the elements are moved out of the aligned position, the detector will no longer receive light generated by the emitter, but rather will receive any form of light available in the environment. It is intended that the subject switch be utilized with any devices where the use of mechanical switches is undesirable.
• the electrical output generated by the photodetector 26 is supplied to a logic circuit means 30, illustrated by the broken lines in Figure 1 and 2.
• the output of generator means 20 is also supplied to logic circuit means 30.
• Logic circuit means 30 is designed such that it will generate a first output signal when the inputs A and B, from the generator and detector means respectively, are similar.
• logic circuit means 30 will generate a second output signal whenever the inputs A and B are different. The first and second output signals can be utilized to indicate whether the elements are in an aligned position.
• detector 26 will generate a similar pulsed output when receiving the pulsed light from the emitter.
• the pulsed output from the detector is supplied to input B of logic circuit means 30.
• input A of logic circuit means 30 is connected directly to generator 20 and therefore is also supplied with a pulsed signal.
• the first output signal is produced.
• the subject switch 10 will generate the first output signal.
• the photodetector 26 will no longer receive the light generated by the photoemitter. Rather, the signal generated by the photodetector will be dependent upon the ambient light in the room. The type of output generated by the photodetector in this situation will be described more fully below. Nevertheless, it is apparent that the output generated by detector 26, and supplied to input B of the logic circuit means 30, will not be similar to .the pulsed signal produced by generator means 20 and
• generator means 20 is intended to produce a continuous series of TTL pulses.
• An example of the pulse train produced by generator means 20 is illustrated in Figure 3A.
• the output signal of generator 20 is supplied directly to input A of logic circuit means 30.
• the frequency of the TTL pulses is on the order of 10 kilohertz.
• the signal supplied to input B of logic circuit means 30 is dependent upon the light received by photodetector 26.
• the transistor network (26, 32) when no light is received by phototransistor 26, the transistor network (26, 32) will be nonconducting. Accordingly, a high or +5.0 voltage signal from source 34 will be supplied to input B, as illustrated in Figure 3B.
• the transistor network (26, 32) when continuous light is received by phototransistor 26, the transistor network (26, 32) will conduct, permitting the current from source 34 to pass to ground. Accordingly, a low or zero voltage signal, as illustrated in Figure 3C, will be supplied to input B.
• the light received by detector 26 is dependent upon ambient light conditions when the telephone is in the off-hook condition, and dependent upon the output from the photoemitter 22 when the telephone elements are in the aligned first position. For example, when the telephone is in the off-hook condition, and the ambient light in the room is insufficient to actuate detector 26, a high or +5.0 voltage signal, as illustrated in Figure 3B will be supplied to input B. In contrast, if the ambient light is strong enough to actuate defector 26, a low signal, as illustrated in Figure 3C, will be supplied to input B.
• the remaining situation concerns the type of signal supplied to input B when the telephone is in the aligned first position, such that the light generated by emitter 22 is received by detector 26.
• the pulsed output from generator 20 is supplied to emitter 22.
• the output from generator 20 is high (e.g. equal to +5.0 volts) no current will flow from source 34 through diode 22. Accordingly, no light will be generated and no light will be received by detector 26 ' .
• a high signal will be supplied to input B.
• a high signal is supplied to input B.
• the subject switch is configured such that when the elements of the telephone are in the aligned position and light from the emitter is received by the detector, the signal supplied to input B follows and is identical to the output from generator 22, supplied to input A.
• Figure 3D illustrates the signal at input B in the latter situation which is identical to the signal at input A as illustrated in Figure 3A. It is to be understood of course that while the path from generator 20 to input B is longer than the path to input A, transmission is virtually instantaneous, such that the signals supplied to the inputs are effectively identical.
• logic circuit means 30 includes an exclusive-or gate 40.
• an exclusive-or gate is a logic device which will generate a low or zero voltage output when the inputs thereto are the same.
• an exclusive-or gate will generate a high or +5.0 voltage signal when the inputs thereto are different.
• Input A of gate 40 is supplied with a continuously oscillating pulsed signal from generator 20 as illustrated in Figure 3A.
• a pulsed signal of identical character, is supplied to input B ( Figure 3D) .
• the signals received at the inputs are either simultaneously high or low.
• the inputs to gate 40 are identical at any given instant of time. Therefore, the output at point C of gate 40 will be
• the signal at input B will no longer be identical to the signal at input A.
• the signal will be either continuously high or low depending upon the ambient light conditions in the room.
• gate 40 at point C, will be the same for either of the continuous signals illustrated in Figures 3B and 3C. More particularly, gate 40 will generate a series of pulses having a frequency equal to the oscillation frequency of generator 20. This result is achieved since the signal at input A oscillates between high and low values, such that it will alternate between being the same and opposite with respect to the continuous signal supplied to input B. Thus, when the inputs are the same, a low signal will be output, and when they are different, a high signal will be output.
• the remaining components of logic circuit means 30 function to convert the oscillating output at point C to a continuous second output signal.
• Integration means 50 consists of a resistor-capacitor network. Resistor-capacitor networks are well known in the art and need not be described in detail. Briefly, the integration means 50 functions to convert an oscillating signal into a level voltage signal. The selection of the component values of resistor 52 and capacitor 54 determine the operating characteristics of the integration means 50. In the preferred embodiments of the subject invention, where generator 20 oscillates at 10 kilohertz, the resistor may be 20 Kohms and the capacitor is 0.1 microfarads.
• Comparator means 60 functions to compare the signal, supplied by integration means 50, with a reference voltage.
• the level of the reference voltage is selected to differentiate between the signals, generated by integration means 50, corresponding to both the on and off-hook conditions. As discussed above, in the on-hook condition, a low level or zero voltage is generated while a voltage of approximately +2.5 volts is generated during the off-hook condition. Accordingly, a reference voltage falling in the range of +1.0 and +1.5 volts is suitable.
• the level of the reference voltage is determined by the values of the voltage divider resistors 62 and 64. In the preferred embodiment, resistors 62 and 64 are 33 and 10 Kohms respectively, which produces a reference level at point 68 of +1.16 volts.
• Comparator 60 functions to generate a low output signal when the voltage at input 70 is less than the reference voltage at input 68. In the alternative, comparator 60 will generate a high signal when the voltage at input 70 is greater than the reference voltage. As discussed above, in the on-hook condition, a low or zero voltage is supplied to input 70 such that a low or first output signal is generated by comparator 60. In the off-hook condition, a 2.5 volt signal is supplied to input 70, which is greater than the reference voltage, such that a high or second output signal is generated. The difference between the outputs can be used to distinguish the on and off-hook conditions.
• the output from a resistor- capacitor integrator will have a slight, but finite ripple.
• a ripple in the signal often results in a degree of uncertainty in the operation of the circuit near the comparator threshold.
• This uncertainty can be overcome by providing the comparator with a hysteresis type characteristic.
• a hysteresis effect can be achieved by coupling a large resistor (not shown) from the output of the comparator to the non-inverting input, thereby creating a positive feedback loop.
• the comparator can be replaced with a integrated circuit, such as a Schmitt trigger, having appropriate characteristics.
• logic circuit means 30 further includes a photodiode 80 to provide a visual indication of comparator output.
• Diode 80 is connected such that when the comparator output is low, corresponding to the on-hook condition, current will flow through diode 80 from source 82 causing the diode to emit light. In contrast, when the output from comparator 60 is high, no current will flow through diode 80 and no light will be generated.
• the signal at input B will not correspond to the signal at input A.
• either a continuously high or low level signal is supplied to input B, depending upon whether the ambient room conditions are dark or light respectively.
• Input A will oscillate between being similar and different with respect to input B, such that the output signal of comparator 40 will be pulsed.
• Integration means 50 functions to convert the pulsed signal from gate 40 into a continuous voltage level which is supplied to comparator 60. Since the voltage level is greater than the reference level, a high or second output signal is generated.
• One of the distinct advantages of the subject switch 10 is that it is operable under all ambient light conditions. More particularly, the on-hook
• o:-. ⁇ - condition will only be indicated when detector 26 receives a pulsed input identical to the output of generator 20.
• the off-hook condition is indicated when any other signal is received at input B.
• a continuous high signal is supplied to input B.
• a continuous low signal is supplied to input B. It makes no difference what type of light is present, such as visible or infra-red radiation.
• the type of light to which the detector is sensitive is irrelevant as long as it is sensitive to the light produced by the emitter.
• the subject switch is also operable in a situation where the ambient light is generated from a pulsed source. For example, some sources generate light at a standard frequency of 60 cycles per second. Thus, in the off-hook condition, a signal having pulsed nodes occurring at a frequency of 60 cycles will be supplied to input B of logic circuit means 30. As can be appreciated, a signal having pulsed nodes at 60 cycles is substantially different from the input of generator means 20 which oscillates between high and low values at 10,000 cycles per second. Thus, even if both signals were coincidently in phase, for each cycle at input B, 150 cycles will be supplied to input A, such that a pulsed output will be generated by exclusive or gate 40.
• the pulses are integrated to produce a voltage greater than the reference voltage resulting in a high output signal from comparator 60. It is apparent that the only light source which will cause a signal to be generated corresponding to the aligned position of the telephone is one which oscillates in phase and at a frequency equal to the output of generator means 20.
• the frequency of the generator means 20 is chosen such that the possibility of encountering ambient light having a similar frequency is eliminated.
• a new and improved switch 10 for indicating whether one element has been removed from an aligned first position relative to another element.
• the subject switch includes a generator means 20 for producing an oscillating output.
• a photoemitter means 22 is provided for generating light in response to input from generator means 20.
• a photodetector means 26 is provided which is disposed in a manner such that light generated by the emitter is received by the detector only when the elements are in an aligned first position.
• the electrical output generated by the detector is supplied to a logic circuit means 30.
• Logic circuit means 30 is also supplied with the output from generator means 20.
• Logic circuit means 30 is configured to output a first signal when the inputs received from the generator and the detector are similar and a second output signal when the inputs are different.

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• Electronic Switches (AREA)

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• 1983
  • 1983-01-04 WO PCT/US1983/000006 patent/WO1983002514A1/en unknown
  • 1983-01-04 EP EP19830900757 patent/EP0097718A1/de not_active Withdrawn

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