335 lines
8.4 KiB
Plaintext
335 lines
8.4 KiB
Plaintext
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PD - POCSAG Decoder
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User Documentation
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Version 1.02 June 1995
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Contents
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1. Introduction
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2. Registration
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3. Installation
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4. Interfacing
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5. Configuration
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5.1 PD.INI
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5.1.1 General Parameters
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5.1.2 Function Codes
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5.2 PAGERS.INI
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5.3 REJECT.INI
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6. Running the program
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6.1 Command Line Options
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6.2 Supported Keys
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6.3 Status Line
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6.4 Normal Mode
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6.5 Debug Mode
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1. Introduction
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PD, together with a receiver or scanner, allows the off-air decoding of
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POCSAG paging signals at either 1200 or 512 bits/second. This makes it
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extremely useful for the testing of paging transmitters and systems.
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Decoding of both numeric and alphanumeric pager data is supported, as is
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the hex dumping of raw POCSAG codewords.
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PD runs on an IBM PC or equivalent, anything from an 8086 upwards. It
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requires 512K of conventional memory and a small amount of hard disk
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or floppy. Hard disk is recommended.
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PD runs from DOS, running from Windows is not recommended.
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2. Registration
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PD is freely distributed as a shareware version. This has a timeout of
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about 5 minutes, after which a registration message is displayed and
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the program exits. Also the logging of pager data to disk is disabled.
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To obtain a fully functional registered copy of PD send a cheque or money
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order for 20.00 pounds sterling to:-
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Peter Baston,
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7 Allerton Close,
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Pen-y-ffordd,
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Clwyd,
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CH4 0NJ,
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U.K.
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3. Installation
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In order to install the program copy the following files into a directory
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on a hard drive, or onto a floppy:-
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PD.EXE Pocsag Decoder program
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PD.INI Configuration file
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PAGERS.INI List of pager codes (7 digit RIC's) to be logged
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REJECT.INI List of pager codes to reject
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PD.TXT This documentation file
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4. Interfacing
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The PD program requires serial POCSAG data to be applied to the CTS pin
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of one of the PC's COM ports. RS232 levels are required, ie at least +/-
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3v. PD is insensitive to polarity, ie it doesn't matter which way up mark
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and space are.
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As POCSAG is transmitted as direct FSK of the VHF/UHF carrier the ideal
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way is to take the data direct from the discriminator, via a data slicer.
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The following circuit, however, has been fairly successful, taking audio
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directly from the receiver's speaker output:-
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0.1 uF |\ +12v
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---||-----------------------|- \|
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AF IN | |741 \
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---- | | /--------------------- Data Out
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| \ ------|+ /| | CTS (pin 5/8)
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| / 100K | |/-12v |
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| \ | | GND ------ GND (pin 7/5)
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GND / ----/\/\/\----
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| | 100K
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| \ N.B. Pin Numbers for com port are
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GND / given as x/y, where x is for a 25
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\ 10K way, y for a 9 way.
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/
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GND
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The +/- 12v for the op-amp can be derived from unused signals on the COM
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port (gives more like +/- 10v but works fine !):-
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TxD (2/3) --------------|<-------------------------------------- -12v
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RTS (4/7) --------------|<-------- GND - -
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| | _ + 1uF
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--------->|------- - - |
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Diodes 1N4148 | - + 1uF GND
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DTR (20/4) ------------->|-------------------------------------- +12v
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5. Configuration
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5.1 PD.INI
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The PD.INI file allows a limited amount of configuration of the PD program.
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Any text editor can be used to edit this file. The file is divided up into
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sections, headed by a name in square brackets, eg [general], [functions].
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In each section are parameters, set to a value with an "=" sign, eg:-
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logbeep=100
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func1=alpha
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5.1.1 General Parameters
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These parameters come under the [general] heading. This version only supports
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one parameter in this section
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5.1.1.1 logbeep
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This parameter allows the length of the "beep", sounded when a pager message
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is logged, to be set. It's format is:-
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logbeep=<number>
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eg:-
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logbeep=100
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Where <number> is the length of the beep in milliseconds. A value of zero
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turns off the beeping, this is the default.
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5.1.2 Function Codes
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These parameters come under the [functions] heading. Four parameters are
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supported - func0, func1, func2 and func3. These allow the decoding of
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the pager data to be determined by the function code, transmitted in the
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address codeword. The format for setting these parameters is:-
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funcx=<string>
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Where <string> is one of:-
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alpha - The message will be decoded as alphanumeric ASCII
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data.
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numeric - The message will be decoded as BCD numeric data.
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raw - The message will be dumped in raw form, as hex
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codewords
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eg:-
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func0=raw
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func1=numeric
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func2=numeric
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func3=alpha
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The program defaults to decoding all function codes as "alpha" data.
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5.2 PAGERS.INI
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This file contains a list of pager addresses to be logged and is simply
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a list of 7 digit RIC's, eg:-
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1234567
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0012345
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etc
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This file may contain up to 100 addresses. Every time one of these
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addresses is encountered it is highlighted on the screen, a beep is
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sounded if configured, and the page is logged to disk with a date/time
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stamp. The log filename is <RIC>.TXT, eg 1234567.TXT.
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5.3 REJECT.INI
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This file contains a list of pager addresses to be rejected, eg to save
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screen clutter. This file has the same format as described in 5.3 above.
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6. Running the Program
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6.1 Command Line Options
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PD is run from the DOS prompt with the following format:-
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PD <-Px> <-B512>
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Where the command line options are:-
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-Px Use COM port x. Default is COM1.
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-B512 Forces 512 bits/second POCSAG decoding, default is 1200 bps.
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6.2 Supported Keys
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The following keys are supported whilst PD is running:-
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ESC Exits the program
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F1 Toggles between NORMAL and DEBUG modes
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SPACE BAR Toggles PAUSE mode on and off
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6.3 Status Line
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After PD starts up it displays a status line across the top of the screen,
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with a data area below. The status line is as shown below:-
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NORMAL COM1 1200 * PD Version 1.02 * PAUSE REJ / 09:30:57
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The items on the status line are described below, from left to right:-
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* NORMAL/DEBUG indicator - shows which mode PD is currently operating in.
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* COM port currently in use.
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* Current POCSAG bit rate.
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* Version of PD being used.
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* PAUSE indicator - appears when paused by the space bar.
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* REJ indicator - appears when a pager address matches one listed in
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REJECT.INI
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* Rotating signal indicator. Appears to rotate when data is being
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received on the correct pin of the COM port. This is no indication of
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good data, just that the levels are correct.
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* The current time from the PC's real time clock.
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6.4 Normal Mode
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In NORMAL mode, as long as good POCSAG data is being received, lines of
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the following form are displayed:-
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[RIC] [Function Code] <data>
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eg:-
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1234567 3 Please call 1234 - 5688
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0345678 1 Test call
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[RIC] is the 7-digit RIC pager address
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[Function Code] is the transmitted function code 0,1,2 or 3
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<data> is numeric,alphanumeric or hex depending on the function code.
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The data field may overflow onto multiple lines.
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Before data is displayed in NORMAL mode the address codeword is checked
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for errors and must be error-free. Subsequent data codewords are not
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checked for errors. Some "garbling" of data may therefore occur if a
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good signal is not being received, although received RIC codes are
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guaranteed to be good.
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6.5 Debug Mode.
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In Debug mode the raw POCSAG codewords are dumped to the screen in hex
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form, eg:-
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7A89C197 7A89CI97 7A89C197 7A89C197 7A89C197 7A89C197 7A89C197 7A89C197
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7A89C197 7A89C197 14083EE2 7A89C197 7A89C197 7A89C197 7A89C197 7A89C197
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Any codewords which do not pass the BCH and parity error checking are
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highlighted. This is very useful for checking the quality of the
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received signal.
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<<<<=====>>>>>
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