INTELLIGENT PULSE TO TONE CONVERTER (CPTI)

Abstract: The Intelligent Pulse to Tone Convertor (CPTI) is an invention to be installed into the telephonic local exchanges (End Office), at the circuit responsible to supply with power (feeding loop circuit) the telephone set after the connections between caller and called parties has been established. The CPTI monitors the telephonic line looking for rotary dial pulses and, if they are present, generates a corresponding DTMF signal and injects it into the telephone line during the interdigital time. The CPTI can sense the rotary dial pulses, using serial, parallel indirect voltage or indirect current sensors. All circuits connected to the telephonic Central Office System should not cause significant insertion loss and interferences. The CPTI even has other features like: fail detection and alarm, serial communication channel, rotary dial differentiated pulses killer and manual reset.

Description: 1 Intelligent Pulse to Tone Converter (CPTI) 2 The Invention provides to the Electromechanical Telephone Switching Systems, 3 the capacity to convert to DTMF (Dual Tone Multi-frequency), the dial pulses 4 generated by an ordinary rotary dial telephone set. The conversion is done only 5 after the call has been successfully completed, that is, after the connections f 6 between caller and called parties have been established. 7 The pulses are created by breaking the current loop from the Central Office 8 Switching System a number of times corresponding with the digit being dialed. 9 Ten DTMF codes can be generated, corresponding to rotary dial numbers 10 0,1,2,3,4,5,6,7,8,9. The limit of DTMF codes is due to the telephone sets and not 11 to the converter (CPTI). If more than 10 pulses were generated the others DTMF 12 sequences (*, #, A, B, C and D) could exist. 13 After the CPTIs are installed in the Telco (Telephonic Company) System, the 14 telephone Users, can access with reliability the various DTMF controlled digital 15 machines; for example: Telemarketing systems, Voice Mail systems, etc., in a 16 transparent mode, without the necessity of replacing the telephone set. 17 The CPTI should be installed into the local exchange (End Office) at the 18 telephone feeding loop circuit (circuit that supplies power to the telephone set). 19 This circuit is activated only after the connections between caller and edited 20 parties have been established. The CPTI should be connected to the points that 21 indicate the telephone line current loop conditions (closed or opened loop). The 22 feeding loop circuits isolate through capacitors the two sides of the telephone 23 line In communication. Each side of a local call receives independent D.C. 24 voltage. Usually the feeding loop circuits are placed into the racks; various racks 25 exist per cabinet. Each rack can accommodate one or more feeding loop circuits, 26 depending on the Telephonic Switching System model. A basic Telephonic 27 Central Office Feeding Loop Circuit is shown as an example in figure 24. The 28 signals Ta.Ra and Tb.Rb are the pair of wires of the Caller and Called parties in 29 communication. 30 To Understand and execute the CPTI project, the professional should have the 31 following profile: to be an electronic engineer with background on the telephonic 32 switching systems, design of analogic and digital circuits and microcontrollers ' 33 programming. For the purpose of description, the circuitry of the CPTI was divided into functional blocks. The functional blocks are also classified as basic or optional, as follows: - Connection (basic) - Pulse Sensor (basic) - Pulse Processor (basic) - Dual Tone Multi-frequency Generator (basic) - Dual Tone Multi-frequency Emitter (basic) - Power Supply (basic) - Clock Generator (basic) - Fail Detector (basic) - Dual Tone Multifrequency Receiver (optional) - Alarm (basic) - Differentiated Pulse Killer (optional) - Initialization (optional) - Shielding (optional) - Serial Communication (optional) The number of blocks, circuit construction type, may be different, depending on the Telephonic Central Office System model, type and requirements (length, r^ck free space, number of feeding loop circuits, voltages, number of optional circuits required, etc.). The electric circuit must be designed to not cause significant insertion loss and interferences to the communication in progress. To design the CPTI for an specific Telephonic Central Office System model, it is very important to obtain the following data: electrical diagram of the feeding loop circuit (circuit activated after the call is completed), inductance and resistance of coils, minimum and maximum loop current, operation and release time of the relays, feeding loop voltage, characteristics of the differentiated pulses, and mechanical dimensions and drawings of the racks. As an example, a CPTI functional block diagram is shown in figure 1. In this case, the CPTI is installed in only one feeding loop circuit. The blocks: Pulse Processor, Fail Detector, Serial Communication ^nd Differentiated Pulse killer, are, in this example, integrated as a microcontroller function. The blocks filled or shaded indicate the optional blocks. The Shielding is shown as a dashed line around the blocks. To design the CPTI with more than one feeding loop circuit, more blocks should be added; for example: Pulse Sensor, Dual Tone Multi-frequency generator, Dual Tone Multi-frequency Emitter and Fail Alarm and the optional blocks, Dual Tone Multi-frequency Receiver, Differentiated Pulses Killer. The Pulse Processor block may or may not be duplicated, depending on the number of I/O ports, operation speed, program memory capacity, read/write memory capacity. The CPTI can be developed according to the function of each block, using digital and analogic electronic components, integrated in one or more components. The circuit should be mounted in a printed circuit board, and the circuits implemented in an independent and individual way. The CPTI may have an Electromagnetic Interference Shielding (Optional) to isolate the circuit from external interferences. The Shielding may be a metallic box wrapping the electronic circuit card, with apertures for led/lamp indicators, to access the reset switches and to pass cables through. There is also a mechanical support to install the CPTI on the rack. The type of the mechanical support will vary according to the Telephonic Central Office System type and model. The interconnection between the Telephonic Central Office System and the CPTI should be through cables and connectors, belonging to the Connection Block. The Connection Block has the function of providing the communication between the CPTI and the Telephonic Central Office System, obtaining the primary power and the Telephonic Central Office System signals to the CPTI, such as: Tip(s) and Ring(s), alarm output, etc. Components like Transzorb, Varistors, Current limiters, fuses, spark-gaps, etc. should be present on the Connection Block for protection against Over-Voltage and Spike. An example of protection circuit is shown in figure 4, and a connector example is shown in figure 3. The Power Supply Block has the function of supplying the CPTI circuit with the operating voltages/currents, preferable through the Main D.C. Power present on the Telephonic Central Office System. The Power Supply may be a simple D.CJD.C. converter with filter and fuse. The D.C. input voltage is dependent on the Telephonic Central Office System operating voltage, usually V=-48V (D.C). The power output voltage and current consumption is dependent on the compo- nents and circuitry, for example, Vout= -5V/20ma. Examples of two DC/DC converters are shown in figures 8 and 9. The Pulse Sensor Block has the role of recognizing the dialed pulses generated by a pulse-type telephone, and of converting them to working logic voltage levels required by the Pulse Processor Block. The Pulse Sensor Block, should not cause interference and introduce significant loss on the telephone line. The Pulse Sensor can be implemented as follows: Serial Sensor: In this case, the sensor is serially installed with the telephonic pair (Tip, Ring), at the Caller and Called(optional) parties. This sensor should have very low impedance. The sensor detects the current flowing at the telephonic pair, through the opening and closing of the current loop. When the loop is opened and closed, a corresponding event signal is generated. As an example, a Serial Sensor may be built using one relay of 1 or 2 coils, with low DC resistance, ex: 20 W,; low inductance, ex:4mH; current sensible, ex: 15ma to I70ma; contact isolation, ex: 1500 VAC; Coils isolation, ex: 1000 VDC. Each current loop event due to pulse dialing makes the relay contacts to close or to open. One of the contacts of the relay may be connected to a reference voltage and the other contact to the Pulse Processor Circuit. A serial sensor circuit example, installed into a typical telephone feeding loop circuit is shown in figure 14. The sensed pulses outputs are logic levels. Parallel sensor: In this case, the sensor is installed in parallel with the telephonic pair of wires, or with one of the wires, at the Caller and Called(optional) parties. The sensor in this case detects the voltage present at the telephonic pair. When the current loop is opened and closed due to a rotary dialing, the voltage is sensed/compared and a corresponding logic signal is generated. The circuit input impedance must be as high as possible, so it does not introduce insertion loss and does not cause interference to the communi- cation in progress. Examples of parallel sensors are shown in figures 15 and 16. It is also important to know that the closed loop voltage varies with the distance of the caller or called parties to the CPTI into the Telephonic Central Office System. For example: monitoring the Ta or Tb in reference to ground, the voltages can be 0V (open loop) and -3V to -24V (closed loop). The output signal from the parallel sensor is connected to the Pulse Processor Circuit. Indirect .Voltage sensor: In this case there is not a contact with the telephonic pairs. The sensor is not hook-up to the telephonic pairs, but reads or monitors instead indirect points of the Telephonic Central Office Switching System, sensible to the current loops. For example, some Telephonic Central Office Switching Systems already have relays, opeτaong *rn , tnθ-Λ)&euureifo6 o open/close current loop; they are required by the Central Office to know if the telephone has been placed on-hook or is still communicating. If the Indirect Voltage sensor reads the contacts of these relays, the resulting signal will correspond to the dialed pulses. A typical circuit present in some CO. Systems, where the Relay coil is also the feeding loop coil to the telephone set, is shown as an example in figure 17. Indirect Current sensor: In this case, there is not a contact with the telephonic pairs. The current sensor reads the looping current from the change of direction of the electromagnetic field generated during a changing of the current flow at the telephonic pairs (example: Pulse dialing). This type of sensor is external to the CPTI and placed around the wire(s) of the telephonic pair. The sensor Uses Hall effect devices, like the ones present at the Tektronix AC/DC Current Probes model A6302, and should have an amplifier circuit plus a converter of logic levels, indicating the presence or absence of the current flowing at the telephonic pair. The output logic signal is connected to the Pulse Processor Block. The implementation of one or another type of sensor will be dependent on the cost, complexity, reliability, installation and Switching System facilities, etc. The sensor can be installed in the Caller and Called side, being the second optional. The Pulse Processor Block has the function of analyzing the incoming pulses from the Pulse Sensor Block and of verifying if they are valid dial pulses. If they are valid, strobe and corresponding dialed digit code should be sent during the inter-digital time, to generate a DTMF signal. An example of a valid dial pulse diagram for a 10 p.p.s. telephone set, is shown in figure 2 and a timing table is shown at table (II). When the telephone is on-hook or the feeding loop circuit is inactive, the flowing current is zero (T5). When the telephone is off-hook and the call is in progress, or the feeding loop circuit is active, there is a current flowing (Example: 1δma) by the telephonic pair (T1). After almost 100ms, when the call is completed, the Pulse Processor Block knows that the communication is in progress, and stays on hold, awaiting an event caused by a current loop in- terruption (T2). When this occurrs (T2), it then awaits a current loop to flow again (T3). In case of valid occurrences, an internal pulse counter is incremented. This counter should be all zeroes (initialized) at the beginning of processing. In multiples occurrences of (T2) and (T3) the counter is incremented and, after recognizing the inter-digital time (T4) the Pulse Processor must generate codes and strobe in accordance with the counter value to the Dual Tone Multi- frequency Generator. An example of code and d i g i t is shown at table (π ι). The period of DTMF generation (strobe) is from 40ms to 215 ms. This Block can be designed with the use of State machines, microcontrollers, etc. The timing values present at table (II) are timing tolerances examples; they are not final or fixed values, and can be changed depending upon request. The Pulse Processor Block In figure 1 , was shown as an Microcontroller part. The pulse is read by one input port and the code plus the strobe are generated by the output ports. The main characteristics to choose the microcontroller are: RAM and ROM memories, I/O ports, internal reset, watch dog timer, timers, etc. The Dual Tone Multi-frequency Generator Block has the function of generating DTMF signals in accordance with the commands received from the Pulse Processor Block. For each generated tone a corresponding code and strobe should be received from the Pulse Processor Block. The generated Tone is -sent to the Dual Tone Multi-frequency Emitter Block. The tone is generated during the Inter-digital time (T4). Figure 18 illustrates an example circuit and figure 19 an example timing diagram of a Dual Tone Multi-frequency generator. Table (IV) shows examples of codes accepted by the DTMF Generator Integrated circuit. The Dual Tone Multi-frequency Emitter Block has the role of amplifying and coupling the DTMF signals generated by the Dual Tone Multi-frequency Generator Block to the telephonic line. The coupling should be preferable by the Called party. When no DTMF is being generated the coupling must be at high impedance and should not cause interference to the communication in progress. Examples of circuits are shown in figures 5, 6 and 7. The Dual Tone Multi-frequency Receiver Block (optional), has the role of recognizing the DTMF signal being generated. The CPTI can compare the command generated with the command read to verify If a correct tone was generated. The Dual Tone Multi-frequency Receiver Block in presence of a valid tone, saves a corresponding code and signals the Fail Detector Block that a valid lone is present. The Fail Detector Block can thus analyze and compare the results. An example of Dual Tone Multi-frequency Receiver circuit is shown in figure 20 and a timing diagram is shown in figure 21. The coupling of the circuit must be in parallel with the telephonic line in high impedance. The function of the Fail Detector Block is to detect functional failures of the circuitry. The detection-and-fail supervision can be implemented at software and hardware level by polling the relevant devices. The most important Blocks to be tested are: Pulse Processor, Dual Tone Multi-frequency Generator and Power Supply. In case of a failure.a command/signal will trigger the Alarm Block circuit. As an example, the Fail Detector Block can be implemented using part of the microcontroller used for other functions with or without the Dual Tone Multi- frequency Receiver Block. The purpose of the Alarm Block is to inform the functional failure by an audible or visual way. The Alarm Block circuit is triggered by the Fall Detector Block and the Telephonic Central Office Alarm System is activated. The failing module/card can thus be found. The circuit can be implemented with transistors, relays, drivers, leds, etc., and an example circuit is shown in figure 23. The function of the Differentiated Pulse Killer Block (Optional) is to add to the CPTI the capacity of attenuating/eliminating the differentiated pulses generated by the rising and falling transitions of the rotary dial pulses. The killed/attenuated differential pulses should not be recognized by equipment monitoring (Click counters) the telephonic line. This Block is installed in parallel with the telephonic line and should be present at both sides of the telephonic line feeding loop circuit. It can be controlled by the microcontroller or other specific circuit, and should be at high impedance when not active. When differentiated pulses are being generated this circuit is activated (Low impedance). Figures 12 and 13 show two examples of differentiated pulse-killer circuits, with the use of a mosfet transistor (analogic switch). When activated the line impedance goes low by placing the resistor or capacitor in parallel with the telephonic line. The differential pulses generated from the rotary dial pulses are shown in figure 2. The Initialization Block (Optional), has the role of initializing the CPTI b a Power-on-reset or by a reset push-button. After being reset, the CPTI is initialized by a self test and awaits rotary dial pulses (Stand-by). An example of circuit is shown in figure 22. The function of the Serial Communication Block (Optional), is to add to the CPTI the capacity of communicating through a serial path (RS232, or other) with a computer system, sending status information and receiving commands (Self test, Tone Generation). The implementation of this Block can be accomplished using part of the microcontroller, used for other functions, plus address micro switches, and line buffers/drivers. A communication protocol patch should be included to the already existing CPTI Software. Various CPTI with different addresses can be present at an unique computer serial channel/port. An example of Serial Communication Block diagram is shown in Figure 22. The Clock Generator Block, has the role of generating and driving all circuit clocks. As an example, this Block can be built using a crystal of 3.58 MHz plus driver ICs. Clock circuits examples are shown in Figures 10 and 11. Although the Intelligent Pulse to Tone Converter (CPTI) here described and referred to in the Block diagrams, circuit examples and tables, may appear the prefered way to implement the invention, it should be understood that several changes may be done without modifying the purpose and the idea of the invention.

Claims: CLAIMS: 1. The Intelligent Pulse to Tone Converter (CPTI) is characterized by to be connected or installed into Telephonic local exchanges (End Office), in the circuit responsible to supply the telephone set with power (feeding loop circuit) after the connections between caller and called parties was established, causing very low insertion loss, to monitor and convert the rotary dial pulses in Dual Tone Multi-frequency (DTMF) during the inter-digital time; 2. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (1 ), is characterized by to have two function types: Basic and optional; 3. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (2), is characterized by having the Basic functions implemented on the follow ing Blocks: Connection, Pulse Sensor, Pulse Processor, Dual Tone Multi-frequency Generator, Dual Tone Multi-frequency Emitter, Power Supply, Clock Generator, Fail Detector and Alarm; 4. The Intelligent Pulse to Tone Converter (CPTI) in ac- cordance with the claim (2), is characterized by to have the Optional functions assembled by the following Blocks: Dual Tone Multi-frequency Receiver, Differentiated Pulses Killer, Initialization, Shielding and Serial Communication; 5. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (1 ), is characterized by to monitor the telephone line in communication, by the caller and Called (Optional) sides; 6. The Intelligent Pulse to Tone Converter (CPTI), in accordance -with the claim (5), is characterized by monitoring the telephone line using Serial, Parallel, Indirect Current or Indirect Voltage sensors; 7. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (1 ), is characterized by generating during the inter-digital time, as soon a rotary dial digit is detected, the corresponding DTMF (Dual Tone Multi- frequency) signal; 8. The Intelligent Pulse to Tone Converter (CPTI) in accordance With the claim ' (1 ), is characterized by injecting the DTMF (Dual Tone Multi- frequency) signal by the Called or by the Caller side of the telephone line; 9. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (1 ), is characterized by its circuit not causing significant insertion loss and interferences when monitoring pulses and when not injecting DTMF signals to the telephonic line; 10. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (3), is characterized by its Power Supply Block being a D.C. /D.C. power converter; 11. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (2), is characterized by all Blocks being implemented using discrete analogic and digital circuits, integrated in one or more components; 12. The intelligent Pulse to Tone Converter (CPTI) in ac- cordance with the claim (3), is characterized by the Fall Detector Block being hardware and/or software, developed to supervise and to detect failures, signaling the fail event by a visual or sonic way; 13. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (4), is characterized by the Differentiated Pulses Killer Block being a circuit that attenuates or kills the differential pulses generated by rotary dialing, decreasing the telephonic line impedance; 14. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (4), is characterized by the Serial Communication Block being composed of a serial interface, micro switches and communication protocol, being capable of sending the status of the CPTI operation and of receiving commands; 15. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (4), is characterized by the Shielding Block being a shield to Electromagnetic Interference; 16. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (3), is characterized by the Initialization Block being composed by a push-button and reset circuit for manual initialization; 17. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (2), is characterized by the Connection Block, being composed by cablβ(s), connector(s) and over-voltage protection circuits, for connection to the Telephonic Central Office System; 18. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (2), is characterized by being assembled and built in accordance with the function of each Block (basic and optional), using analogic an digital components, assembled in a printed circuit board, with shape and size variable with the number of optional circuits included; 19. The intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (3), is characterized by the Dual Tone Multi-frequency Generator Block being composed by a circuit that, upon receiving a code, strobe and a 3.58 MHz clock, generates a DTMF signal; 20. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (3), is characterized by the Pulse Processor Block, being composed of a dedicated circuit or microcontroller or State-machine, capable of processing the incoming rotary dial pulses generating strobe and codes for tone generation; 21. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (3), is characterized by the Dual Tone Multi-frequency Emitter Block, being composed by an amplifier and telephone line coupling circuit; 22. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (3), is characterized by the Clock Generator Block being composed by a 3.58MHz clock, used mainly for DTMF generation; 23. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (4), is characterized by the Dual Tone Multi-frequency Receiver Block being composed by a DTMF Receiver, capable of recognizing DTMF signals and of generating the DTMF presence signal and its corresponding code; 24. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (6), is characterized by the Serial Sensor being a low impedance current monitor, serially connected to the telephonic line; 25. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (6), is characterized by Parallel Sensor being a high impedance voltage monitor, connected in parallel with one or both wires of the telephonic line; 26. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (6), is characterized by the Indirect Voltage Sensor being a voltage monitor; installed at relay(s) contact(s), or points that show the telephonic line current loop condition; 27. The Intelligent Pulse to Tone Converter (CPTI) in accordance with the claim (6), is characterized by the Indirect Current Sensor being a Hall Effect current monitor, installed around the telephonic line, without electrical contact.

Inventors: DE ALMEIDA FERRAZ DANILO, GONCALVES PAULO ARTUR, DE ALMEIDA FERRAZ, DANILO, GONCALVES, PAULO, ARTUR
Applicants: ALMEIDA FERRAZ DANILO DE, GONCALVES PAULO ARTUR, DE ALMEIDA FERRAZ, DANILO, GONCALVES, PAULO, ARTUR
Application year: 1993
Main classification: H04Q1
IPC codes: H04Q1