WO2009010481A1 - Serial bus system for use in elevators and other lifting apparatus or the like - Google Patents

Abstract

A serial bus system for control and/or signaling devices of elevators and other lifting apparatus or the like, wherein the control and/or signaling devices generate and/or are adapted to receive pulses coded according to a serial protocol, characterized in that said protocol provides single-wire, non differential low-frequency transmission referenced to a single common ground.

Description

Serial bus system for use in elevators and other lifting apparatus or the like

The present invention relates to a serial bus system for use in elevators and other lifting apparatus, which comprises various control, check and signaling devices (typically push-buttons, audible or visible signaling devices , sensors , intercoms for emergency communications) directly connected to the bus , and an interface board for communication with said system, which is expressly designed for "universal" use, i.e. adapted for easy installation to any elevator without requiring any significant change to the electric part, or for "dedicated" use, i.e. designed for optimized connection to a certain type of control panel .

In the art of elevators and lifting apparatus in general, it is known to use control devices, most simply push-buttons held in appropriate push-button panels, to send a request to the elevator motion controller, also known as control panel, to move the car to a given floor. Such devices are located both outside the hoistway, like in the case of floor buttons and inside the car, like in the case of car buttons. As a user presses a push-button, an electric circuit closes and off/on information is transmitted along a cable to the control panel , which reads such information and operates the required actuators to move the elevator to the desired floor. Pressure of a given button is typically confirmed by the energization of a lamp or a LED, generally located in the button or proximate thereto. Particularly, the control panel transmits the information to the corresponding lamp once the elevator motion request control has been received. This information is carried by a conductor that connects the control panel to the corresponding lamp or LED to be turned on.

Considering that an elevator typically has a large number of push-buttons and that various types of signaling devices may be provided, possibly integrated with light emitting displays of various types, for example indicating the position of the car during its travel, complex wiring is required for this type of systems, involving a large number of conductors, particularly at least one for each push-button and for each signaling device, wherefore manufacturers and part dealers have been long looking for solutions to optimize end/or minimize wiring, in view of a simpler and faster installation of these systems and lower labor costs.

One common solution to reach these purposes is the pre-wiring technique, which consists in equipping all the parts of the electric system of the elevator that require a large number of connections (push-button panels, displays contacts within the hoistway or car, control panel) with quick connectors and providing long cables cut to size according to the characteristics of the system, and terminated at each end with quick connectors mating with those provided on the devices . While this affords shorter installation times when everything works properly, serious drawbacks may occur if cable is shorter than required on site. Also, while installation of the system is very easy and does not require specially skilled personnel , thereby meeting an increasingly frequent requirement, typical failures of such systems are very difficult to handle: for example, for cables to be laid in the hoistway, tens of meters long cables are required to be dropped down from above . Therefore , connectors are likely to be subject to high tensile stresses and will be thus prone to false contacts throughout their life, thereby inherently affecting system reliability. Drawbacks associated with the above technology are also caused by the large physical size of the connectors , which often exceeds the size of their holes , and require masonry works or, even worse, cable breaking and re-wiring on site, with consequently longer installation times. For these and other reasons many installers do not use this technology and would rather opt for traditional system wiring.

Another prior art solution is serial communication. Pre-wiring has the purpose of ensuring faster wiring, but cannot reduce the number of conductors . Serial communication affords conductor number reduction, but involves higher costs. This is because, in currently available serial solutions, interface boards are required to be mounted to the push-button panels or proximate to the devices to be "serialized", for converting parallel on/off signals from normal push-buttons and normal signaling devices into the serial protocol that is used by the relevant system. The addition of these "parts" involves additional costs, wherefore it is commonly acknowledged that the serial solution is only cost-effective with systems having a given number of stops, typically at least 6 or 7 stops. In these systems, high costs are associated with the boards to be mounted in the pushbutton panels at each floor (the so-called "external" push-button panels) , wherefore many installers opt for "mixed" solutions , and only use serial arrangements for panel/cab communication, while leaving hoistway cables in parallel . In any case, while these serial systems reduce the number of conductors in the communication lines , they still cannot reduce the total number of connections and even increase it, considering the parallel connections required between the normal devices (push-button panels, displays, etc.) and serial communication interfaces, said interfaces being an "additional part" to be connected, positioned and managed. These boards are sometimes bulky and cannot be easily fitted in the push-button panels or wireways . Thus, any savings derived from optimized wiring are often nullified by the need of installing additional enclosures for these boards in the hoistway, which increases complexity and affects reliability of the system.

Most of serial communication systems for elevator applications are based on or derived from standard protocols. This involves the use of transmission rates that are much higher than those actually required, also due to the overheads of the protocols being used, designed for other application fields. Therefore, complex and costly hardware is required, which also has a relatively large size, and anyway too large a size to allow all serial communication circuits to fit in one push-button. The requirement for high-rate links causes these protocols to use a differential-type transmission at physical level. This kind of transmission has the advantage of supporting high transmission rates, but only when special types of cables with adequate terminations are used. The advantages of differential transmission can be only utilized using a twisted pair cable. This type of cable can be easily used for the hoistway (with the external i.e. floor push-button panels associated therewith) , but cannot be easily used between the control panel and the car, where car motion imposes the use of a particular kind of cable, known as "flexible cord". Also, the twisted pair cable cannot be used in old systems, wherefore existing conductors might not be used for renovation. One more drawback of differential transmission in elevators is common mode noise. While the use of twisted pair cable nullifies differential noise induced in the cable due to variable external electromagnetic fields, which justifies the high transmission rates that can be obtained over differential lines , the high ground path impedance typical of control circuits in differential lines causes potentially destructive common mode overvoltage to be likely to occur: since elevators include switching devices (inverters and switching power supplies) for controlling the winch motor, the door operators, etc., and since elevators have a large extension in space, local common mode overvoltage is likely to occur, due to high frequency phenomena that act as "charge pumps", and to cause the failure of integrated circuit designed for serial communication. In addition to the above mentioned problems, that cause noise from within the system and can thus be estimated and accurately evaluated during design, and possibly solved, there still exists the problem of external perturbations that can be even of large amount. For example, in case of lighting, such common mode overvoltage is induced in the lines that differential line drivers are likely to be destroyed, such components being based on the use of operational amplifiers .

While common mode noise can be mitigated by using efficient shield patterns, this would constitute an additional complication during installation, and involve a further loss of reliability. For instance, if the shield breaks even at one point (due to mechanical stresses, oxidation, loosening of a terminal, false contact of a plug-in connection) , the whole shielding arrangement can become inefficient. Furthermore, it is highly unlikely that a common elevator operator, that has no special skills in microelectronics , transmissions, shielding, can localize and correct a fault. Furthermore, these high-rate differential lines require termination resistors. This is because transmission occurs at high frequencies, with significantly short wavelengths as compared with physical cable extensions. Therefore, signal reflection at the end of the line can generate contributions that can cause interference with the transmitted signal, thereby corrupting transmission. The reflection problem can be solved by terminating the line at both ends with a resistor having a resistance value that matches the characteristic impedance of the line, which depends on the type of cable being used. This resistor produces the virtual effect of an infinitely long line and eliminates reflections. Nonetheless, these termination resistors constitute an additional problem for reliability and proper operation of the system: any wrong connection thereof would affect reliability of transmission and any later damage thereto might prevent the system from properly operating, and in any case these resistors are an additional problem for installers .

The high transmission rates, and the need for impedance adaptation, as well as the need to determine beforehand the values of the termination resistors to be added, involve the selection of a special kind of cable to be used, because such cable shall have a characteristic impedance that matches the resistance value of the terminators being used. Therefore, only the particular type of cable selected during design can be used, and system reliability considerations would prevent installers from using solutions that would be more suitable on site.

Conversely, the system of the present invention, which is based on a single-wire, non differential, low- frequency (of KHz order) transmission referenced to a single ground (wire "-" of the serial bus) is affected by none of the above problems: due to low-rate transmission, the wavelengths of transmitted signals cause no reflection problem, wherefore termination resistors are no longer required and any type of cable can be used. Such low-rate transmission is also associated with self-inductance and stray capacitance values that are negligible in terms of signal reliability, wherefore large section cables, i.e. virtually any cable typically used in this type of systems, may be used. Also, since our transmission operates at widely spaced logical levels (0/12 V relative to bus ground) we'll have very high noise allowance, which affords high inherent transmission reliability, further enhanced by the low ground path impedance of the bus lines, ensuring quick dissipation of any noise induced in the line due to external causes, and hence making such noise negligible. A further advantage consists in that all the devices connected to the bus share a common ground ("-") , all signals being referenced thereto. Nothing is even floating in this configuration, wherefore no overvoltage that might damage communication circuits as described above may occur. Bus power supply "+" and "-" is controlled, filtered and conditioned, wherefore enhanced reliability is obtained as compared with equivalent buttons of traditional type because if the latter are susceptible of being burnt if they are controlled by the control panel with a wrong voltage, unlike serial devices that receive power directly from the bus . Obviously, further single-wire transmission systems exist. Some of them are more complex than is strictly required for our purposes. Others are very simple but do not contain line arbitration techniques and cannot implement transmission over a bus. Particularly, there are transmission systems based on wave edge counting, which have been only used for broadcast mode-display control, without involving line arbitration and management policies , or for simple point-to-point connections. On the other hand, single- wire protocols use communication data packets organized in frames, which contain a few bits for routing to the target device, more bits for the message to be transmitted, one or more parity or error-check bits. These protocols provide the advantage of allowing management of very complex systems, i.e. having a large number of peripheral nodes and of reaching high reliability levels , by increasing redundancy and the number of error-check/detection bits, although much information has to be transmitted over the line, and high bit rates are thence required, which involves either the same problems as in differential transmission, or a slower response by the system, i.e. poorer performances. Nonetheless, in both cases complex, costly and bulky circuits would be required, which could not be integrated in the push-buttons . Finally, certain manufacturers use a point-to-point transmission with multiple wires, typically a multi- phase clock, an input data wire, an output data wire. The clock phases define a frame, with the transmissions of the other two lines being synchronized therewith. The system provides the advantage of being very simple, but it still requires the use of an additional clock wire and does not implement line arbitration techniques , and hence does not form a bus .

As compared with the other single-wire transmission systems, the following additional advantages are achieved: 1) transmission is not organized in frames, which are susceptible of being degraded due to noise, in which case troubleshooting and later re-transmission would be required, thereby adding complexity to the system (in both hw and sf terms) and especially cost increase ;

2) transmission is strictly unidirectional, different wires being used for different communication directions .

Especially thanks to the latter point 2 , we can use a very simple information-carrying technique which simply consists in counting "short" square wave fronts along the line, while setting as a start and as an end two square waves , i.e. a high square wave and a low square wave (or vice versa) having several times longer duration. Such coding arrangement, in combination with the digital low-pass filter that removes the spikes, allows signals to be transmitted in a virtually clean band (obviously with reference to the particular circuit configuration of the bus , which is characterized by a low ground path impedance) . Therefore, transmission is wholly reliable, no difference being noticed in terms of information carrying performance, as compared with normal pushbuttons having respective connecting wires .

The combination of all the above arrangements allows surprising firmware optimization, and consequently provides the advantage of using ultra- cheap controllers, that can be fitted in each pushbutton with no significant cost increase: the routine that is used to read and interpret the serial sequence only requires 34 code lines and 3 RAM registers. The low-pass software filter only requires 21 code lines and 3 more RAM registers. Further inexpensive parts include: a resistive divider for line reading; a Darlington NPN transistor for transmission, i.e. control to ground. These few parts implement a bus, with all elements connected in parallel therewith, which ensures higher performances than many of currently available serial systems, or at least performances equivalent to the traditional condition in which each push-button/signaling device is connected by its own wire. The cables or wires are allocated, cut to size and ready for use, otherwise serial solutions are provided, in which additional interface boards are provided with normal push-buttons or signaling devices connected thereto, i.e. characterized in that they contain a normal contact and a normal lamp- or led-based signaling device. While the above solutions represent natural developments of the traditional wiring system, they still suffer from a number of drawbacks. The prewiring arrangement requires prior knowledge of exact cable lengths before on-site installation, and is susceptible of causing serious installation problems whenever the cable paths are required to be other than expected. Thus, cables are provided in greater lengths than is strictly required, and this generates bulk problems as many "narrow" systems do not have enough space for accommodating excess cable length. Also, the presence of multiway connectors of considerable size complicates cable laying in many cases , for example when cables are required to pass through walls and masonry works are to be avoided. Further drawbacks include reduced system reliability (the pre-wired system is subject to strong tensile stresses during Laying, whereupon false contact problems are likely to occur) and difficult troubleshooting (no contact is usually accessible for measurement because all connections are established by quick connectors) . On the other hand, while traditional serial systems can fulfill the purpose of reducing the total number of wires from the control panel to the peripheral devices , they still cannot reduce the total number of connections and even increase it because, in addition to the connections between the serial board and the normal devices (typically one wire for each contact and one wire for each signaling device, in addition to "common" wires) , connections are to be provided between the serial board and the bus , as well as between the interface that may be mounted in the control panel and the control panel itself. However, should the system be already integrated in the control panel, flexibility would be affected because the downstream part of the system would be useless whenever a different kind of panel should have to be used. Also, serial boards involve additional costs, space requirements and constitute an additional part of the system that is subject to failure. While the above technologies have been increasingly used in recent years, they are still not universally widespread. The pre-wired arrangement is mainly used in new systems, preferably scaffold-mounted systems, which allow accurate cable length estimation beforehand. Nonetheless, certain installers would opt for a traditional wiring arrangement which allows them to keep the whole system under control, and reserve the possibility of making changes to it at a later time, especially upon customer's request. On the other hand, the traditional serial arrangement is deemed to be advantageous on systems with a certain number of stops, usually at least 6 or 7 stops, and is rarely totally relied upon. Thus, the serial arrangement is only used for car calls and registered call signaling or for displays .

The object of the present invention is to provide a system for control and/or signaling devices of elevators and other lifting apparatus or the like, which requires simple and effective wiring with a small number of conductors and no additional boards and uses "intelligent" devices, which are themselves equipped with a serial interface.

The invention fulfils the above object by providing a serial bus system expressly designed for control and/or signaling devices of elevators and other lifting apparatus or the like, which has a highly simple design, so that all electronic communication circuits may be integrated in the devices, particularly in the pushbuttons, without any considerable cost increase as compared with an equivalent traditional device (such as a normal button containing a normal contact and a LED indicator) , wherein the control and/or signaling devices generate and/or are adapted to receive pulses encoded according to a protocol, particularly a serial protocol. At physical level, this bus uses four wires as a base, i.e. two power wires and two signal wires. Power supply ("+" and "-" wires) is a controlled and filtered 12 VDC, the two signal wires ("M" and "S" respectively) are used for receiving controls from control devices and for transmitting signaling information to signaling devices respectively. When looking at the system from the panel side there are actually two wires , one for reception and one for transmission. 12 V square waves are transmitted over the wires , and are referenced to the ground of the system ("-" wire) . When idle, the lines are held high by pull-up resistors contained in the interface board for the control panel . Square waves are obtained by "pulling to ground" the line using a npn transistor, typically a darlington transistor. Then, signals are collected from the various nodes connected to the bus by resistive dividers, which adapt the voltages to the TTL logic values requested by the controllers . In ordinary applications , the "M" line is controlled by the peripheral devices and the interface "listens" to it (i.e. there is transmission from the field to the interface, and reception by the interface) ; the "S" line is controlled by the interface and the peripheral devices listen to it (i.e. there is transmission from the interface to the field, and reception by the devices) . In fact, the "M" line is continuously monitored by the devices due to the line arbitration algorithm being used, which is of a "pure ALOHA" algorithm with continuous listening to the line. At protocol level, what actually carries information is the number of square wave edges (rising, falling edges or both, according to the applications) which are counted from a start of transmission signal, and are evaluated as an end-of transmission signal is detected, said signals being uniquely recognizable. These two signals are characterized in that they have several times longer duration as compared with the square waves used for code transmission. Therefore, a wholly asynchronous communication is obtained, which is insensitive to any clock drifts im the individual devices, that might be caused by their simultaneous engagement in other processes (such as when displays are simultaneously engaged in screen refreshing) , thereby affording a higher inherent cost-effectiveness of these devices , because one controller can simultaneously handle multiple functions . The square waves have frequencies of the order of one KHz for push-button actuation signals and for light-emitting button refreshing signals and of the order of 200 Hz for display refreshing signals .

The code reading system uses a "threshold algorithm", in which: a) The line is sampled (possibly with a variable sampling rate, depending on the processor workload) b) the high samples ; the low samples and the edges are counted c) if the low (or high) samples exceed a given threshold, then the edge counter is reset d) if the high (or low) samples exceed a given threshold, then an edge value output is given, and counting restarts. This reading algorithm is implemented at any node in which bus reading is required, i.e. the interface (which reads the "M" line) , the intelligent pushbuttons (which read the "S" line) , the displays (which read the "S" line or the "SD" line) . This algorithm is not inherently resistant to spikes (of periodic or non periodic nature) , because spikes have the peculiarity of changing the number of edges. Accordingly, a low pass digital filter has been implemented, which is introduced in software form in the microcontroller between the line reading routine and the serial sequence interpretation routine . This filter has a cut-off frequency which is very accurately set to a slightly higher value than the typical frequency of square waves acting as information carriers . Thus , any periodic or non periodic spikes are eliminated and any resulting damage is prevented. Therefore, such low-pass filter avoids any wrong reception. However, should the start- or end-of transmission signals be disturbed, nothing would be simply received on the other side. Later on we will discuss the transmission policies that have been proposed to ensure clear and unexceptionable operation of the system. Line arbitration is handled by an algorithm known as "pure ALOHA" with continuous listening to the line. In accordance with this algorithm, the intelligent push-buttons continuously listen to the "M" line to check whether it is free (i.e. idle, or high) . When a push-button is pressed and has to transmit its code, transmission occurs if the line is free. Then, if transmission was successful, i.e. if it was not interrupted due to collisions or noise, the button leds are turned on for about one second to indicate that the button has been pressed and transmission has occurred. Conversely, if the line was found to be busy, the button does not start transmission to prevent collisions with other transmissions in progress, and attempts transmission again after a pseudorandom time until the operation is successful. Thus, all transmissions are queued over the line, based on their order of arrival. Since noise- or collision-corrupted transmissions are abandoned and the receiving station releases the interpreted code when it detects the end- of-transmission signal, any corrupt transmission is ignored by the receiving stations, thereby effectively avoiding any false controls .

Since idle lines are silent, the system response time exactly matches the serial sequence transmission time (which in turn depends on the transmitted code) , when the line is idle. If multiple controls are imparted at the same time (such as in the case of multiple buttons being pushed at the same time) , a queue is formed over the line, and all the controls are transmitted one by one, in order of time of acquisition.

Proper control acquisition feedback by the receiving board is indirect. The button that transmitted the code is turned on for a moment if noise- or collision-free transmission has been ascertained, but no direct feedback by the receiving board is provided in the system, to confirm proper control reception. However, indirect feedback is provided, because when the control panel receives a control, it turns on the relevant signaling device. Therefore, feedback is given by the control panel. In view of the above description of system operation, the only problematic event that might occur is that the receiving station ignores the transmission because the end-of-transmission word has been corrupted. In this case, the user presses the push-button and sees that nothing happens, and then presses it again. It should be noted that the provision of a feedback system in the transmission protocol would be redundant and burdensome and would affect system performances. Also, it was experimentally found that the occurrence of ignored controls was very rare.

In certain variants of the system, more wires are used for additional purposes, as discussed hereafter. In further variants of the system, signals with different metrics are transmitted over the same wire. Information concerning controls and signaling is serially carried over two conductors , and no special requirement is imposed thereupon, wherefore any pair of conductors normally used in traditional systems may be used herein. The use of control and signaling devices including intelligent interfaces for managing serial communication allows such simplified wiring arrangement, and ensures cost-effectiveness in any case, even in systems with a small number of stops and when pre-wiring is used anyway. Thus, instead of using one conductor for each signaling and/or control device, each of such devices simply includes a communication interface, for properly encoded information to be serially exchanged with the control panel using a single conductor. Information encoding allows the control panel to identify the control origin or the signaling destination without the need of decoded information carried over parallel communication lines . While a single conductor may be used for exchanging both controls and signaling information, the strength and reliability of the system may be increased by the use of at least two conductors, for physical separation of controls and signaling information. Thus, any error that might affect a control, possibly due to noise, has no effect on the corresponding signaling information .

Control devices are typically push-buttons or keypads and signaling devices are lamps or leds . All of these devices are of intelligent type, which means that they are equipped with circuits designed for management of serial communication with the bus with which they are interfaced. Such management is designed to be integrated in each relevant device for maximized system simplification. This advantage owes to the simplicity of the communication protocol, which is actually based of pulse trains, and allows use of simple communication circuitries that can be easily fitted inside the pushbuttons . The push-buttons are advantageously backlighted. Lighting is actuated by corresponding encoded signaling transmitted over the signaling wire whereas the button state is transmitted with proper encoding over the control wire to the control panel. Particularly, the backlighted buttons are the floor or car buttons that are used to call the elevator to a floor. The signaling device is actuated by the control panel of the elevator to confirm that the button has been pressed.

According to a particular embodiment, the system has 5 wires . The additional wire is used for controlling advanced signaling devices , such as displays, speech synthesizers or the like. These devices are also equipped with circuits designed for management of serial communication with the bus with which they are interfaced. Particularly, the protocol uses 3 wires for controlling the advanced signaling devices , two of which are for power supply . The third wire may also be the signaling wire, with information being exchanged in multiplexed form to devices of different types. As used herein, the term power supply shall be intended in its more general meaning, including either two voltages of opposite sign, or a ground and a positive or negative voltage, as those of ordinary skill in the art may easily appreciate.

According to a particular embodiment, the system has 6 wires . The additional wire is used to manage control/check devices at the elevator car roof. These devices are also equipped with circuits designed for management of serial communication with the bus with which they are interfaced. Particularly, the protocol uses 3 wires for controlling the car roof control/check devices , two of which are for power supply . The serial communication protocol is typically based on pulse trains whose duration and number change according to their encoding, which is based on start- and end-of transmission words for maximized communication hardware simplification, although more advanced communication forms may be also used, such as pulse code transmissions over a carrier, such as PCM (Pulse Code Modulation) or the like. While the system has no particular safety requirement, because it does not affect vital operating functions of the elevator, its reliability and strength are an important issue. Any periodic disturbances induced by the inverters of the mechanical drive and any random spikes essentially caused by relay switching, may cause the control panel to receive wrong controls and/or the signaling devices to receive incorrect signaling information, with apparent problems for the operation of the whole system. Such errors are eliminated by a low-pass digital filter implemented in software form in the microcontrollers that manage device operation, such filter has a cut-off frequency slightly higher than the transmission frequency so that any periodic or random glitch over the line can be eliminated and only the good signal is allowed to pass. It shall be noted in this respect that transmissions occur at much lower frequencies than typical frequencies collected by the line, wherefore this filtering arrangement is highly effective. Redundant error-check arrangements may be also used, although they will affect the simplicity and response rate of the system.

According to another aspect, the invention relates to an interface board for the serial bus system. The bus system allows operation of control and signaling devices of any elevator with a small number of wires . Nevertheless, the control panels and more generally the control circuits of the existing elevators are adapted to receive controls and transmit signaling information in parallel, i.e. using one conductor for each device concerned by the control or signaling information. Particularly, the inputs of these panels are designed to receive DC voltages of ON/OFF type from traditional buttons , and the outputs are designed to transmit voltages to the signaling lamps or leds , generally by closing/opening of relays . For such a panel to be interfaced with the bus system of the invention, either an interface has to be used which can adapt the inputs and outputs to the communication protocol or the communication circuitry of the panel has to be redesigned. The second option requires the development of control panels specially dedicated to serial communications and is certainly feasible especially for new installations, nevertheless in view of reducing costs by using standard components currently available or already installed in a system to be renovated, the invention provides an interface board for communication with the bus system, which allows interfacing with traditional control panels by emulating control and signaling devices of traditional type, i.e. simply equipped with one contact. For this purpose, the interface board of the invention comprises an electronic circuit adapted to receive controls and/or transmit signals over the serial bus , an electromechanical circuit adapted to receive controls and/or transmit signaling information from/to the control panel of the elevator. The electromechanical circuit comprises at least as many output relays as there are push-buttons connected or connectable to the serial bus and at least as many optically isolated inputs as there are signaling lamps connected or connectable to the serial bus .

By this arrangement, the serial system ensures maximized transparency both to the user who notices that the control and signaling devices have the same operation as equivalent traditional ones, and to the control panel which finds at its terminals the same electric values and the same behaviors that would be found with equivalent traditional control and signaling devices . A controller is preferably provided within the board, which is programmed for converting input controls via the serial bus into corresponding relay actuation controls so that pressure of different buttons causes the actuation of different output lines that are or can be interfaced with the control panel . Similarly, different signaling lamps are or can be actuated in response to control signals on different inputs that are or can be interfaced with the control board, a controller being provided, which is programmed for converting said inputs into corresponding signaling information over the serial bus .

The board is preferably provided in combination with an electronic or electromechanical control panel, having parallel inputs/outputs adapted to receive/transmit decoded controls/signaling information, although it can be also designed for interfacing with a control panel having a small number of inputs/outputs . In this case, information is exchanged between the board and the panel with partial encoding. According to another embodiment, a microprocessor circuit is provided, which communicates with the interface and the control panel for providing transcoding of controls/signaling information over the serial bus to/from the interface board into corresponding controls/signals to/from the control panel. Instead of or in combination with such microprocessor circuit a non volatile memory containing the transcoding codes is provided. In this embodiment, the number of output lines to the control panel is lower than the number of buttons connected or connectable to the serial bus and the number of input lines from the control panel is lower than the number of signaling lamps connected or connectable to the serial bus, because the interface board exchanges information with the control panel in encoded form. This solution may be used for new installations in which the control panel may be replaced or an existing panel may be adapted for at least partial reception/transmission of encoded information. In the most advanced solution, the control panel already contains the circuitry required for bus interfacing, e.g. has an interface board integrated therein. Since the circuitry dedicated to communication with the control panel is totally separated from the serial bus management circuitry within this interface board, panel-specific communication protocols may be implemented in the board, without the restrictions involved by bus management timing.

According to another aspect, the invention relates to a method for modifying an elevator system comprising floor buttons and car buttons and signaling lamps connected in parallel with a remote control board. The method includes the steps of disconnecting the control board, the buttons and the lamps from the system, replacing said buttons and said lamps with buttons/lamps of intelligent type having circuits specially designed for management of serial communications to/from the remote control board using a first conductor for transmitting controls and a second conductor for receiving signaling information, said first and second conductors being selected from existing system conductors. The method further includes the step of introducing an interface board as described hereinabove between the control board and said buttons/lamps, and connecting it to said conductors to form a system according to the invention.

Further features and improvements will form the subject of the dependent claims.

The features of the invention and the advantages derived therefrom will be more apparent from the following detailed description of the annexed drawings , in which:

Fig. 1 shows an exemplary view of a bus system of the invention in its 5-wire configuration with light- emitting displays . Fig. 2 is an exemplary view of the types of signals used in the system of the invention.

Fig. 3 shows a system configuration with floor keypads and buttons connected to an interface board.

Fig. 4 shows the interface board of Fig. 3 connected to a traditional control panel that is able to manage up to 24 stops.

Fig. 5 is an enlarged view of the interface board of the previous figures .

Fig. 6 shows a 3-wire system for connection of advanced displays and signaling devices and relevant interface boards .

Fig. 7 is an enlarged view of the interface board of Fig. 6. Fig. 8 shows an application example with a keypad, a LCD display and a speech synthesizer in the car.

Fig. 9 shows a 6-wire system with car roof interfacing. Fig. 10 shows a wiring diagram of an intellingent button .

Fig. 11 shows an exemplary wiring diagram of a dual microcontroller interface board.

Referring to Figure 1, the system of the invention 1 is suitable for managing a 6-floor elevator system having advanced light- and voice-emitting signaling devices. Particularly, the system has 5 wires, designated as +, - M, S, D respectively, with the floor buttons 101, the car buttons 201, the floor keypad 301, the car display 401 and the voice synthesizer 501 interfacing therewith. The buttons are all of the light-emitting type, which means that they can be turned on when they receive appropriate signaling from the control panel (not shown) which also interfaces with the bus as better explained hereafter. The operation is the same as in any traditional elevator: by pressing a push-button, a user reserves the car to his/her floor. The light-emitting displays show the car position in real time, both at the floors and inside the car, whereas the speech synthesizer is actuated to indicate the car stop floor, to prevent careless users from skipping the stop or coming out at the wrong stop.

In a traditional system, each push-button would require two wires (one for sending the pressed button signal and the other for turning on the lamp integrated therewith) in addition to power supply wires . With the system of the invention, each light-emitting button is connected to the power supply (+ and - wires) in addition to two wires only (M and S) shared by all buttons , wherefore 4 wires only are used for interfacing all system buttons. Particularly, the wire designated as M is the control wire, i.e. the line that carries a button pressing control to the control panel. The wire indicated by S is the signaling wire, i.e. the line that serially carries the lamp energizing controls for each push-button of the control panel .

Since the devices are connected in parallel , identification of the particular device that transmits the controls and receives the signaling information is allowed by the communication protocol and particularly by the type of signals that circulate over the bus . Fig. 2 shows a typical signal carried over a signaling and/or control wire in a "granted" logic state (upper half of the diagram) or "denied" logic state (lower half of the diagram) . A low logic signal corresponds to a line that has been pulled to ground, and a high value corresponds to a line that has been pulled up towards the power supply voltage. Code transmission occurs by the transmission of n Tb sequences, separated by an easily recognizable start-of-transmission sequence (Ti) and an end-of-transmission sequence (Tf) . Bus timing (Tb, Ti, Tf) may change according to system configuration and the signals may be modulated, e.g. amplitude-modulated. Particularly, two or more modulations with different bus timing arrangements may be provided over the same line, for different signals to be transmitted over the same line. For example, the signaling line may be also employed for refreshing the display, no separate line being used therefor. For this purpose, display refresh may use a transmission with 10 times slower timing than the one that is used for button lamp energization. Thus, although the two transmissions occur over the same conductor, they do not interfere with each other because a start or end sequence of one of them is interpreted as a non valid signal by the other class of devices, and vice versa. Otherwise, as shown in the configuration of Fig. 1, the displays can be managed by an additional system wire. This conductor, designated as D, is the display wire, i.e. the dedicated line that carries the controls for advanced output devices, namely the two displays 301 and 401 and the speech synthesizer 501. By this arrangement, signaling, controls and advanced information are carried by independent conductors S, M, D and the strength and reliability of the system is thus increased.

More complex system may include additional lines, in addition to lines M, S and D, for managing more devices , such as for car roof device control , as discussed below with reference to Fig. 9, or for two- way amplitude-modulated audio signals, to be used, for instance for self-dialing emergency calls.

Referring to Fig. 3, keypads 601 and intelligent buttons 201 are connected to a bus system having 4 wires only (+, - , M, S) . The control panel (not shown) is connected to the bus via the interface board 2 , which has the circuitry required for management of serial communication over the bus . The board 2 , which may also obviously be part of a circuit located on the control panel or elsewhere in the system, has a power supply input 102, a terminal block 202 with optically insulated inputs for signaling, a terminal block 302 with outputs, each having a relay 402, for controls and the connector 412 for connection to the 4 bus wires. Each button/keypad has a corresponding terminal for connection of the 4 bus wires .

Fig. 4 shows the same system as Fig. 3, interfaced with the control panel 3. The keypads have been omitted for simplicity. The inputs 202 and the outputs 302 are connected in parallel with corresponding outputs 103 and inputs 203 of the control panel 3 respectively. In this example, the system is designed to manage up to 24 light-emitting push-buttons . The operation may be summarized as follows . The interface board 2 (as shown in greater detail in fig. 5), which receives power via the connector 102, supplies power to the bus, particularly to the + and - conductors, and to its logic. Each time that a button is pressed, the board 2 decodes the serial information received by the M conductor through the microcontroller 502 and actuates the corresponding output relay 402. Thus , the control panel can receive the control into the corresponding input line 203 already in decoded form. Like in the case of the control panel 3 operating one of the lines 103 to transmit an energization control to the corresponding lamp, this decoded information reaches one of the inputs 202 of the interface board which uses the microcontroller 602 to transmit the encoded information onto the signaling wire S so that the corresponding lamp can interpret such information as a corresponding energization control .

The interface board 2 also includes diagnostic leds 712 and pushbuttons 812 for manual call control. In one embodiment, the interface board 2 has holes 912 for sandwiched connection with an additional board 4 for display management and with advanced communication devices via the D conductor of the bus . Such display board for may be also integrated in the interface board two or separate therefrom, for example to be directly connected to the control board. Figure 6 shows how the display board 4 is connected with the interface board 2 and with the advanced devices . The latter particularly include the speech synthesizer 501, the matrix displays 301, 111 and 411, the 7 segment displays 311 and 211 and the LCD 511. In this figure, the + and - power supply signals are designated as AL and CL and the D signal is designated as SD (serial display) . Each device is connected in parallel to the bus via these three wires . The display board 4 , which is shown in enlarged form in Fig. 7, is equipped with a microcontroller 104 for supervising serial communication management and exchange of information with the interface board 2 or directly with the control board 3. Displayed information includes the floor number 204, arrows for additional signaling 304 and auxiliary signaling 404, such as alarms, on corresponding connections 702, 802, 902 with the interface board 2.

Fig. 8 shows an application example with a keypad, a LCD display and a speech synthesizer in the car, which are interfaced with a 4-wire bus. In this case no fifth wire D is provided because the LCD display 511 and the speech synthesizer 501 are directly serially controlled by the keypad 601 via dedicated wires 611, 612, for further simplification of the system. The user selects a floor number by the keypad 601. The selected number 511 appears on the display 511 and the synthesizer 501 converts it into speech. No communication with the control panel is needed here, wherefore the use of a dedicated display wire would unnecessarily increase costs and complexity. The keypad ensures intelligent supervision of advanced devices before transmitting the control to the control panel as explained above.

Referring now to fig. 9, the system of the invention includes a 6-wire bus. The sixth wire, designated as TC, is used for managing car roof devices, such as door opening and closing contacts, operator control relays , magnetic proximity switches for car position control, various stop contacts, various safety contacts. In this case, the interface board 2 has a small number of inputs/outputs . This is a "dedicated" arrangement, in which the bus system is integrated in the system. Particularly, the control panel 3 only has 4 inputs 603 and 4 outputs 503 as information is exchanged between the interface board 2 and the panel in coded form. While this solution is suggested in the 6-wire system embodiment, it can be also used in systems having a different number of wires , particularly 3 , 4 or 5 wires .

Using transcoding tables, a microprocessor and non volatile memory devices, the controls/signaling information over the serial bus to/from the interface board 2 are changed into corresponding controls/signals to/from the control panel 3. In this embodiment, the number of output lines to the control panel is lower than the number of buttons connected or connectable to the serial bus and the number of input lines from the control panel is lower than the number of signaling lamps connected or connectable to the serial bus, because the interface board exchanges information with the control panel in encoded form. This solution may be used for new installations in which the control panel may be replaced or an existing panel may be adapted for at least partial reception/transmission of encoded information. In the most advanced solution, the control panel 3 already contains the circuitry required for bus interfacing, e.g. has an interface board 2 integrated therein.

Fig. 10 shows a simplified wiring diagram of an intelligent push-button which is designed to be interfaced with the system of the invention via +, - , M, S conductors. The core of the circuit is the microcontroller UO and the transistor Ul which is controlled by the output GPO of the microcontroller UO and pulls to ground (designated as -) the M line, which is normally held high by a pull-up resistor located, for instance, in the interface board 2 to be installed in the control panel 3. Furthermore , there are a resistive divider R4 , R5 for providing the S line to the microcontroller, and a resistive divider R6, R7 for providing listening to the M line to the microcontroller. The line management algorithm that is implemented in the microcontroller is a sort of "ALOHA" algorithm with continuous listening to the line. Before speaking to the line, the button listens to it to see if it is busy, in which case it delays transmission by a pseudorandom time. Whenever a collision or noise occurs during transmission (which is detected by continuous line monitoring, and by intercepting the difference between what has been transmitted and the listening results) , transmission is abandoned and restarted after a pseudo-random time. The signal from the S line is collected by the divider R4/R5 and provided to the port GP2 of the microcontroller. Then, it is low-pass filtered by a software routine implemented in the microcontroller for eliminating any spurious signals, and passed onto the serial sequence interpreting routine . The circuit of Fig. 10 finally has a pair of leds Ll , L2 mounted in series and controlled by the output GP4 of the microcontroller UO via the transistor U3 and a traditional button SWl connected to the input GP3 of the microcontroller UO and to the derived voltage VDD, via the divider Rl , R2 from the power supply + , inputs .

Fig. 11 shows a simplified wiring diagram of the control and check section of the bus of an interface board of the invention. The two controllers U_TX, U_RX are used for transmission and reception management respectively, for improved system reliability. Nonetheless, it shall be understood that one controller may be also used for the purpose. The M (reception) ad S (transmission) lines of the bus are held high by the two pull-up resistors R6, R5. The M line is connected to ground by the individual buttons as explained above with reference to figure 10, whereas the S line is connected to ground by the interface, via the transistor Tl controlled at its base by the output RB5 of the microcontroller U_TX. Digital noise filtering is provided, which is implemented by software means in the microcontrollers. Particularly, low-pass filtering is used.

Obviously, the invention is not limited to the above description and figures, but may be greatly varied, especially as regards construction, without departure from the inventive teaching disclosed above and claimed below. With reference to the above, further variants of the inventive system as described in greater detail above may provide the use of an additional wire in the bus , for two-way audio communications between the car/hoistway/shaft and the machine space, or between the car/hoistway/shaft and the assistance call center, which may be reached through a public telephone network via RTG or GSM connection.

In one particular embodiment, modulations will be provided in analog form and will be normal amplitude modulations .

In another embodiment, these audio signals will be digitized and transmitted in digital form.

Also, in yet another embodiment, the audio signal is modulated over the "+" wire of the bus that is used for power supply.

These embodiments require the development of both intercommunication systems and talk-listen switches that can be connected to the serial bus and: a) an interface for connecting currently available dialing pads with the above system; b) a novel dialing pad, designed for connection to the universal serial system.

Advantageously this dialing pad is of GSM type. Since the GSM technology allows transmission and reception of both audio and data messages, particularly in SMS form (short text messages) and since this GSM device would be wholly connected to the serial bus and able to exchange information with the other apparatus connected thereto, use of SMS might be integrated within the features of the elevator.

For example, a zone of the LCD display might be customizable via SMS, with one SMS being sent to the elevator SIM, for the message text to appear on the display. Also, alert SMS messages might be transmitted by the system when certain situations occur. This would require no additional conductors, because system state information is already available and ready to be transmitted over the serial bus .

Further implementations include the use of broadband UMTS technologies . Interfaces may be also provided to Ethernet systems using standard TCP/IP protocols , to create PC-based elevator monitoring systems. Interfacing between the universal serial system and the Internet will also provide remote elevator monitoring applications using the Web for connection. Also, since a digital audio signal is already available, it might be transmitted over the Web using Voice-Over-IP technologies, wherefore software for making telephone calls over the Internet, such as Skype , may be used for emergency communications , which would make GSM solutions out-of-date. In this case, the system would be equipped with Internet-based remote elevator monitoring means , involving two-way audio/video communication over IP. If hardware includes intelligent, i.e. microprocessor- or PLC-based means, then these means may consist, on both system- and assistance center-sides, of microprocessors or PLCs with remote elevator monitoring software loaded or loadable and thus executable therein, operating over the web by two-way audio/video communication over IP.

Claims

1. A serial bus system for control and/or signaling devices of elevators and other lifting apparatus or the like, wherein the control and/or signaling devices generate and/or are adapted to receive pulses coded according to a serial protocol, characterized in that said protocol provides single- wire, non differential low-frequency transmission referenced to a single common ground.

2. A system as claimed in claim 1, characterized in that the transmission frequency is of KHz order.

3. A system as claimed in claim 1 or 2, characterized in that the encoding serial protocol has logic levels with spaced voltage values , of the order of 0 V for the low or ground value to 12 V for the high value .

4. A system as claimed in one or more of the preceding claims , characterized in that the bus lines have a low ground path impedance .

5. A system as claimed in one or more of the preceding claims, characterized in that it uses four wires, i.e. two for power supply (+,-), one (M) for receiving controls from the control devices, one (S) for transmitting signaling information to the signaling devices .

6. A system as claimed in one or more of the preceding claims , wherein the control devices include push-buttons , keypads or similar means of intelligent type, having circuits specially designed for managing serial communications with the bus with which said control devices are interfaced.

7. A system as claimed in one or more of the preceding claims , wherein the signaling devices include lamps, leds or similar means of intelligent type, having circuits specially designed for managing serial communications with the bus with which said signaling devices are interfaced.

8. A system as claimed in one or more of the preceding claims , wherein the control and/or signaling devices include push-buttons with light-emitting means, said light-emitting means being actuated by corresponding encoded signaling over the signaling wire (S) , the push-button state being transmitted in encoded form over the control wire (M) .

9. A system as claimed in claim 8, wherein the push-buttons with light-emitting means are floor or car buttons that are used to reserve the elevator to a given floor, signaling being actuated by the control panel of the elevator to confirm that the button has been pressed, said control panel being interfaced with the bus .

10. A system as claimed in one or more of the preceding claims, wherein 5 wires are provided, the additional wire (D) being used to control advanced signaling means , such as displays , speech synthesizers or the like, said devices having circuits specially designed for managing serial communications with the bus with which they are interfaced.

11. A system as claimed in claim 10, wherein the protocol uses 3 wires (+, - , D) for controlling the advanced signaling devices , two of which are for power supply (+, -) .

12. A system as claimed in claim 11, wherein one of the wires is a signaling wire (S) , the protocol allowing multiplexing of information addressed to different types of devices over the same conductor.

13. A system as claimed in one or more of the preceding claims, wherein 6 wires are provided, the additional wire (C) being used to manage the elevator car roof control/check devices , said devices having circuits specially designed for managing serial communications with the bus with which they are interfaced.

14. A system as claimed in claim 13, wherein the protocol uses 3 wires (+, - , C) for managing the car roof control/check devices , two of which are for power supply (+, -) .

15. A system as claimed in one or more of the preceding claims , wherein the serial communication protocol is based on pulse trains whose duration and number change according to their encoding, which is based on start- and end-of transmission words.

16. A system as claimed in one or more of the preceding claims , wherein the communication protocol uses pulse code transmissions over a carrier.

17. A system as claimed in one or more of the preceding claims, wherein the transmission protocol is unidirectional, different conductors being used for different communication directions, i.e. for communication with different users .

18. A system as claimed in one or more of the preceding claims , characterized in that the information is encoded by generating a predetermined number of square wave edges over the line, the train of square waves being delimited by start and end words consisting of a high and a low square wave or vice versa, and which square waves of the start and end words have different durations , preferably longer than information encoding information, the edges of information encoding information between the start and end limit square waves being counted during code reading.

19. A system as claimed in one or more of the preceding claims , characterized in that the two (M) and (S) wires, designed for signal transmission and reception respectively are used for transmitting/receiving 12 V square waves referenced to the ground ("-" wire) and held high, when idle, by pull-up resistors, whereas the square waves are obtained by pulling to ground their respective lines

(M, S) using a npn transistor, typically a darlington transistor.

20. A system as claimed in one or more of the preceding claims , characterized in that code reading is performed using a threshold algorithm which operates as follows: it samples the line; it counts the high samples , the low samples and the edges ; when the low or high samples exceed a given threshold it resets the edge counter and if the high or low samples exceed a given threshold then it gives an edge value output and restarts counting, said means that operates with said reading method or algorithm being provided at each unit or node, such as any push-button, any display and any other interface that reads the signals passing over the bus .

21. A system as claimed in one or more of the preceding claims , characterized in that it has line arbitration means with an algorithm known as "pure ALOHA" with continuous listening to the line, whereby the intelligent buttons continuously listen to the line to check whether it is idle, i.e. high, wherefore if the line is high, i.e. free, when a push-button is pressed, a code is generated and transmitted and a check is performed to see whether transmission was successful, i.e. not interrupted due to collisions or noise, and such state is indicated by optical means, such as a button led, whereas if the line is low, i.e. busy, or transmission was unsuccessful, then the serial interface means of the intelligent button repeat transmission after a pseudorandom time generated by a special generator as many times as is needed for successful transmission to occur.

22. A system as claimed in one or more of the preceding claims, wherein at least one noise filtering device is provided on the communication lines .

23. A system as claimed in claim 22, wherein said device includes one or more digital low-pass filters.

24. An interface board for a serial bus system as claimed in one or more of the preceding claims , characterized in that it comprises an electronic circuit adapted to receive controls and/or to transmit signaling information over the serial bus , an electromechanical circuit adapted to receive controls and/or transmit signaling information from/to the control panel of the elevator, said electromechanical circuit comprising at least as many output relays as at least there are push-buttons connected or connectable to the serial bus and at least as many optically isolated inputs as there are signaling lamps connected or connectable to the serial bus .

25. A board as claimed in claim 24, wherein a controller is provided, which is programmed for converting input controls via the serial bus into corresponding relay actuation controls so that pressure of different buttons causes the actuation of different output lines that are or can be interfaced with the control panel.

26. A board as claimed in claim 24 or 25, wherein different signaling lamps are or can be actuated in response to control signals on different inputs that are or can be interfaced with the control board, a controller being provided, which is programmed for converting said inputs into corresponding signaling information over the serial bus .

27. A board as claimed in claim 26, wherein the controller is the same that converts button actuation controls into relay actuation controls .

28. A board as claimed in one or more of the preceding claims 24 to 27, characterized in that it is provided in combination with an electronic or electromechanical control panel, which has parallel inputs/outputs for receiving/transmitting decoded controls/signalling information.

29. A board as claimed in one or more of the preceding claims 24 to 27, characterized in that it is designed to be interfaced with a control panel having a small number of inputs/outputs , information being exchanged between the board and the panel in coded form.

30. A board as claimed in claim 29, wherein a microprocessor circuit is provided, which communicates with the interface and the control panel for providing transcoding of controls/signaling information over the serial bus to/from the interface board into corresponding controls/signals to/from the control panel .

31. A board as claimed in claim 30 , wherein a non volatile memory containing the transcoding codes is provided instead of or in combination with the microprocessor circuit.

32. A board as claimed in one or more of the preceding claims 29 to 31, wherein the number of output lines to the control panel is lower than the number of buttons connected or connectable to the serial bus and the number of input lines from the control panel is lower than the number of signaling lamps connected or connectable to the serial bus .

33. A system as claimed in one or more of the preceding claims 1 to 23, characterized in that it is provided in combination with an interface board as claimed in claims 24 to 32.

34. A method for modifying an elevator system comprising floor buttons and car buttons and signaling lamps connected in parallel with a remote control board, the method including the steps of disconnecting the control board, the buttons and the lamps from the system, replacing said buttons and said lamps with buttons/lamps of intelligent type having circuits specially designed for management of serial communications to/from the remote control board using a first conductor for transmitting controls and a second conductor for receiving signaling information, said first and second conductors being selected from existing system conductors.

35. An intelligent button for serial bus-based signal transmission systems characterized in that it comprises a push-button and electronic means for interfacing with the lines of a serial communication bus , which interfacing means include a communication line management program of such type that the interface operates as a sort of "ALOHA" algorithm with continuous listening to the line, whereby: before transmitting signals to the line, the button listens to it to see if it is busy, in which case it delays transmission by a pseudorandom time, whereas whenever a collision or noise occurs during transmission (which is detected by continuous line monitoring, and by intercepting the difference between what has been transmitted and the listening results) , transmission is abandoned and restarted after a pseudo-random time.

36. An intelligent button as claimed in claim 35, characterized in that it comprises a push-button connected to a circuit for interfacing with a serial bus line, such as a line comprising conductors (+, - , S, M), which circuit comprises a microcontroller (UO) and a transistor (Ul) which is controlled at its base by the output (GPO) of the microcontroller (UO) and pulls to ground (designated as - in the figure) the line (M) , which is normally held high by a pull-up resistor located, for instance, in the interface board

(2) to be installed in the control panel (3) .

37. An intelligent button as claimed in claim 35 or 36, characterized in that it comprises a resistive divider (R4 , R5) for providing the line (S) to the microcontroller, and a resistive divider (R6, R7) for providing listening to the line (M) to the microcontroller.

38. A system as claimed in one or more of the preceding claims , characterized in that the bus comprises an additional line for transmission/reception of two-way audio communication signals between the car/hoistway/shaft and the machine space, or between the car/hoistway/shaft and the assistance call center, and means for interfacing said communication line of the bus with one or more public communication networks such as the public telephone network via RTG or GSM, UMTS and/or Internet connection.

39. A system as claimed in one or more of the preceding claims , characterized in that modulations of the audio communication signal are of analog type, and are particularly normal amplitude modulations .

40. A system as claimed in one or more of the preceding claims 1 to 38 , characterized in that audio communication signals are digitized and transmitted in digital form.

41. A system as claimed in one or more of the preceding claims , characterized in that the audio signal is modulated over the "+" wire of the bus that is used for power supply.

42. A system as claimed in one or more of the preceding claims , characterized in that it comprises , as a peripheral device, an intercommunication system for transmission/reception of audio signals having an interface for connection to the serial bus .

43. A system as claimed in one or more of the preceding claims , characterized in that it has an interface for connecting normally available dialing pads to the serial bus .

44. A system as claimed in one or more of the preceding claims , characterized in that it includes a dialing pad with an integrated interface for connection to the serial bus .

45. A system as claimed in one or more of the preceding claims , characterized in that it has means for generating, transmitting and receiving text messages, so-called SMS messages, the serial bus communication interface having means for transmission/reception of text messages to/from one or more of the other apparatus connected to the serial bus .

46. A system as claimed in claim 45, characterized in that it has a display in the car and/or panel of each floor, with a customizable zone, said zone being connected with a unit for receiving the text signals transmitted over the serial bus and said receiving unit controlling the display of the text message/s in said zone of the display, whereby a SMS message may be transmitted to the SIM of the elevator system and the transmitted text may appear on the display.

47. A system as claimed in one or more of the preceding claims, characterized in that the system comprises a unit for generating and transmitting messages, which are alert messages generated and/or transmitted under certain operating conditions as monitored by sensors and/or diagnostic detection units.

48. A system as claimed in one or more of the preceding claims, characterized in that it comprises a serial bus interface to an Ethernet network using standard TCP/IP protocols.

49. A system as claimed in one or more of the preceding claims , characterized in that it comprises system monitoring means which uses remote computer- controlled stations, such as remote PCs.

50. A system as claimed in claim 49, characterized in that it comprises at least one remote station for monitoring the operating conditions of the system, comprising a microprocessor or a central processing unit (CPU) in which an elevator monitoring application is loaded or loadable and executable, said remote unit being connected to the system via the Internet.

51. A system as claimed in one or more of the preceding claims , characterized in that the two-way audio signal is communicated in digitized form through the Internet using Voice-Over-IP technologies.

52. Internet-based remote elevator monitoring software with two-way audio/video communication over IP, wherein the operating conditions of the elevator system are monitored from a remote station over the Web and speech, audio and possibly video communication is managed by an Over IP protocol.