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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING FSK standard number identifier. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Telephony At present, with the introduction of modern digital exchanges, the CUP caller ID service is becoming more and more accessible. The most widespread is the CUP service in the FSK (frequency modulation) standard, which allows you to transmit to the subscriber not only the caller's number, but also other information. An extended version of this Multiple Data Message Format (MDMF) standard will be described here in a concise form. For more information, see ETS300659-1 and ETS300659-2 of the European Telecommunications Standards Institute (ETSI). In the FSK standard, data is transmitted at 1200 bps. Logical unit (MARK) is encoded with a frequency of 1300 Hz, logical zero (SPACE) - 2100 Hz. Information is transmitted byte by byte, each byte begins with a SPACE start bit and ends with a MARK stop bit. Up to ten stop bits can be added between bytes. A generalized transmission timing diagram is shown in fig. 1.
Information is transmitted between the first and second ringing signals, the duration of the pause T1 is 500 ... 2000 ms, the duration of the pause T2 is at least 200 ms. The message transmission is preceded by the CHANNEL SEIZURE signal (channel capture), which is a sequence of 300 alternating bits 0, 1 ... 0, 1 or 30 bytes 55H. The duration of this signal is 250 ms. Then follows the MARK SIGNAL signal, consisting of a block of logical units with a duration of 180 ± 25 ms or 80 ± 25 ms at the choice of the operator. Next comes the message itself (MESSAGE). The message is a set of parameters. Each parameter consists of three fields. The first field is the parameter type, it is a single byte in HEX format that tells the Caller ID device how to interpret the next two fields. The second field is the length of the parameter (also bytes), this is the number of data bytes in the third field. The third field is parameter data, these are ASCII codes in accordance with CCITT recommendations, while the most significant bit is always 0. A typical message format is shown in fig. 2.
MESSAGE TYPE (message type) - for the extended format is 80H. MESSAGE LENGTH (message length) is the number of bytes in the message, excluding the MESSAGE TYPE, MESSAGE LENGTH and CHECKSUM bytes, expressed as one byte. PARAM. 1 TYPE - date and time parameter, equal to 01Н. PARAM. 1 LENGTH - length byte of this parameter, always 08H. PARAM. 1 DATA - information about the date and time of the incoming call, transmitted in the following sequence: month tens byte O or 1, month units byte from 0 to 9, days tens byte from 0 to 3, days units byte from 0 to 9, hours tens byte 0 to 2, hour unit byte 9 to 0, tens minute byte 5 to 0, minute unit byte 9 to XNUMX. This parameter is optional and may not be passed. PARAM. 2 TYPE - caller's number parameter, equals 02H if the number is transmitted. PARAM. 2 LENGTH - length byte of this parameter. PARAM. 2 DATA - the caller's number itself, transmitted in ASCII codes, starting with the most significant digits, the maximum length is 20 bytes. This parameter is required and is always passed. However, if the caller has Caller ID Restriction enabled, PARAM. 2 TYPE is 04H, PARAM. 2 LENGTH is 01H and PARAM. 2 DATA is equal to the ASCII code "P" ("Private"). If the caller's station does not support the CLIP transmission protocol, then PARAM. 2 TYPE is 04H, PARAM. 2 LENGTH is 01H and PARAM. 2 DATA is equal to the ASCII code "0". PARAM. 3 TYPE - caller's name parameter, equals 07HEX if the name is transmitted. PARAM. 3 LENGTH - length byte of this parameter. PARAM. 3 DATA - caller's name, transmitted in ASCII encoding, maximum length 50 bytes. This parameter is optional and may not be passed. If the PBX transmits this parameter, but the caller has blocked the transmission of his name, then PARAM. 3 TYPE is 08H, PARAM. 3 LENGTH is 01H and PARAM. 3 DATA is equal to the ASCII code "P". See also PARAM. 3 DATA is equal to ASCII code "0" in case. if the caller's name is not available for any other reason. CHECKSUM is a checksum byte that is the modulo 256 binary complement of the sum of all message bytes, starting with MESSAGE TYPE, excluding the CHECKSUM byte itself. This protocol does not provide error correction, and if the checksum is not equal to zero, the message is discarded. The list of transmitted parameters is determined on each exchange. The standard provides reserved parameter codes for use by a particular telephone operator. Parameters can be passed in any order. To ensure compatibility, unknown parameters are discarded by the Caller ID device. If the message contains mutually exclusive parameters, only the first one is used. The simple SDMF (Single Data Message Format) format is a special case of the extended format and is rarely used today. In this format, only two parameters are transmitted - date-time and subscriber number. The message type is 04HEX. The table byte by byte considers an example of transmitting the number 246-58-31 at 20 hours, 45 minutes, December 26, indicating the reason for the absence of the caller's name.
I suggest readers to repeat my own design of the Caller ID prefix, which is compatible with SOME and MDMF formats. The operability of the design has been tested on real telephone lines. The device is connected in parallel to a telephone set in a telephone line with a voltage of linear batteries of 48...60 V. It is characterized by ease of control, reliability of number identification, extremely low power consumption from the power source and from the telephone line. The set-top box does not interfere with the operation of faxes, answering machines and other devices operating in automatic mode, and meets the requirements of standards for connecting subscriber devices. Structurally, it can be made in a separate case or built into a telephone set. The device is powered from a battery of three AA or AAA size galvanic cells or from a 4...5 V battery. The batteries are constantly recharged with low current from the line. The current consumption from the telephone line with the handset in standby mode (at Ipit = 4,5 V) is not more than 0,1 mA, while the recharging current of the power source is not less than 0,01 mA. The average current consumption from the power source in other modes is no more than 1 mA. The scheme of the device is shown in fig. one.
The memory capacity of the set-top box is sixty-three incoming numbers. Memory is organized on a first-in, first-out basis. Two buttons SB2 ("Previous") and SB3 ("Next"), you can "flip through" the memory in the direction of earlier calls and in the direction of late calls. The number, time and date of the call are stored in the memory. Economical use of memory is provided, i.e. if the same subscriber calls you with a frequency of less than 10 minutes, then his number is recorded in memory once and the time of the last call is recorded. When the power is off, the information in the memory and the operation of the clock are stored for at least 3 minutes (depending on the capacitance of the capacitor C8), which is enough to replace the batteries. The number of new calls recorded in the memory since the last viewing of it is displayed on the indicator. The counter of new calls is reset after viewing the memory. The set-top box is controlled through a menu of three functions: Alarm setting, Clock setting and Clear memory. Entering the function menu is by pressing the SB1 ("Function") button. The basis of the device is the PIC16F628 (DD1) microcontroller. FSK decoding is done in software. One of the built-in comparators is used, the outputs PA1 and PA2 are its inputs. The reference voltage is formed by the circuit R2R3R4, the resistor R3 sets the offset between the inputs of the comparator 10...15 mV. The cascade on the transistor VT1 is the simplest comparator for analyzing the ringing signal. The PB0 pin of the DD1 controller is configured as an external edge interrupt source. The R9VD4 circuit, when a telephone line is connected, recharges the GB1 battery with a current within 10 ... 20 μA. Zener diode VD5 protects the power supply circuit from possible overvoltage. It is advisable to use imported zener diodes with a good slope characteristic, the total consumption depends on this. For the sound accompaniment of pressing the buttons, an HA1 sound emitter with a built-in self-oscillator for an operating voltage of 6 or 12 V is used. If sound is not required, the HA1 emitter can be omitted. Chip DD2 in this design is used only as a clock, timer, calendar and alarm clock. Flash-memory 24C08 (DD3) is used to store the determined numbers. Each number has 16 bytes. The information is recorded in binary decimal format, i.e. 4 bytes are allocated for the date and time of the call, and 12 bytes are allocated for the number with a maximum length of 24 digits. Chips DD2 and DD3 interface l2C connected to the controller DD1. When the power is turned on, the registers of the controller DD1 and the clock DD2 are initialized. The timer of the DD2 chip is set to an interval of 7 s. After that, the device goes into standby mode, the controller executes the SLEEP command. It can be activated by one of the following events: a front at the PBO input (incoming call), a change in the state of the PB4, PB5 inputs (pressing buttons or a pulse at the INT DD2 output), pressing the SB1 button (controller reset). The program analyzes the type of reset, and if it is a "hot" restart (button SB1), then the menu of functions is entered. With a period of 7 s, a pulse appears at the INT pin of the DD2 chip, according to which the controller reads the minutes and hours registers from the DD2 chip and loads the HG1 indicator with these values. This prevents the indicator from automatically switching to stopwatch mode. In standby mode, the ratio of controller active time to SLEEP time is 1:7. On an incoming call, the first ring of the exchange activates the DDI controller, the FSK message is decoded and buffered. The received code is analyzed, displayed on the indicator and written to memory in BCD format. After that, the controller goes into standby mode. In the mode of viewing the memory of incoming calls, pressing the buttons activates the controller, information about the number, time and date of the call is selected from the memory and displayed on the indicator. The number is displayed for two seconds, the date and time of the call are displayed for the next two seconds. This cycle is repeated three times, then the device goes into standby mode. The incoming call mode takes precedence over the memory browsing mode. Entering the function menu, i.e. reset has the highest priority. The device is assembled on a single-sided printed circuit board (Fig. 4).
Before mounting the elements, it is necessary to install a jumper passing under the microcircuit terminals. Capacitor C1 must have a capacitance in the range from 0,022 to 0,047 microfarads and be designed for an operating voltage of at least 250 V. The capacitance of capacitor C3 can be from 4700 to 10000 pF. To set up the device, you need a conventional multimeter (preferably digital), an oscilloscope with an input impedance of 10 MΩ, and a battery of cells or batteries with a voltage of 4,5 ... 4,8 V to power the device. You will also need a thin screwdriver with an insulated handle to adjust the trimmer capacitor C7. When properly assembled from serviceable components, the device starts working immediately and you only need to check the operation of the VT1 comparator and the current consumption. DO NOT CONNECT THE SET-TO-BOX TO THE TELEPHONE LINE UNTIL THE POWER IS ON! Turn on the power 4,5. .4,8 V via a milliammeter pre-set at a measurement limit of at least 5 mA DC. After about 5 seconds, the set-top box will go into standby mode (the indicator will show the time and the counter of calls), the current consumption should not exceed 50 μA. If the current is greater or the set-top box does not go into standby mode, it is necessary to check the quality of the installation, the controller firmware and the VD5 zener diode. In standby mode, every 7 seconds the controller regenerates the indicator, so the readings of the milliammeter increase briefly. We turn on the power directly (without a milliammeter), connect the leads of the VD1 diode bridge (intended for the telephone line) to the line, turn on the milliammeter in the gap of one of the wires. The prefix must be in standby mode, while the current in the measured circuit must not exceed 100 μA. Now you need to check the operation of the comparator VT1. We connect the conclusions of the diode bridge VD1 directly to the telephone line. With an incoming call, the output of the PBO controller should have pulses that are close to rectangular in shape. The last stage of adjustment is to adjust the accuracy of the clock with capacitor C7. Do this during operation. If the clock "runs", slightly turn the rotor C7. Repeat this operation until you achieve an accurate clock. Use a dielectric screwdriver, as adding capacitance to the oscillator circuit of the DD2 microcircuit can lead to its malfunction. The microcircuits used are sensitive to static electricity, so use a "grounded" soldering iron with a power of no more than 40 watts isolated from the mains. Perform all installation operations with the power off. A few words about how to manage the console. Button SB2 "Prev." leafs through the memory in the direction of earlier calls, and the SB3 button "Next." - towards the later ones. The prefix will show the number, date and time of the call, and after that it will automatically switch to standby mode. To enter the settings menu, press and release the SB1 "Function" button. Use the SB3 button to select a function. To enter the function, use the SB2 button. F1 - setting the alarm. From left to right, the alarm switch symbol will appear on the indicator ("-" - the alarm is off, "P" - the alarm is on) and the hour and minute values. To select a value, use the SB3 button, to change - SB2. To exit the function, press the SB3 button for at least 0,5 s and release. F2 - setting the time and date. The display will show the date, month, hour and minute from left to right. To select a value, use the SB3 button, to change - SB2. To exit the function, press the SB3 button and hold it for at least 0,5 s, and release it at the signal of the exact time. F3 - clearing the entire memory of numbers. Entering this function, you have 10 seconds to confirm the operation with the SB2 button. Exit - automatically. No other settings are required. Controller code fsk6.zip. The configuration word is contained in the HEX file. Author: V. Bachul, Chisinau
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