The DCF-77 time of transmission and radio frequency Mainflingen near Frankfurt, Germany. The DCF-77 time may be used by devices to provide a precise reference time. Timing of the computer equipment, such as NTP server systems, providing a precise point of reference for computer networks may use the program as an external source of accurate time. This article describes how the DCF-77 can be decoded to provide a reference to a specific timetable for NTP servers and other computer timing applications.
Before describing the format of the transmission, it is worth remembering a little 'about the history of the issuer. German national standard time and frequency radio, called DCF-77 is in operation since 1959. The spread is currently managed by T-Systems, a division of German telecommunications company Telecom Deuce. Precise information about the course of the show is produced by a cesium atomic clock maintained by the German National Physics Laboratory. The transmitter has a power of 50W, which can be received up to 1900 km from Frankfurt. The reception can be easily obtained in most of central and north-west. The transmission is transmitted as amplitude modulation, pulse width encoded data signal. Information about the hours of streaming, repeated every minute. The data is transmitted as a series of 59 pulses, one pulse per second. Each pulse represents a bit 'of data or a binary zero or binary. One hundred milliseconds pulse represents a binary zero, while the pulse is two hundred binary millisecond. The pulses can be decoded at the end of the date of the minutes and hours.
Timing information is represented in the DCF-77 transmission encoded binary coded decimal. Data bits are encoded into the carriage as follows. Data bits 1 to 14 are reserved for future improvements. Bit 15 indicates that the transmitter in operation today - the main transmitter or backup transmitter. 16 bit is the announcement of the return of summer. 17 bits indicates if DST is currently in use. Bit 18 indicates the time standard and is the inverse of 17 bits. Bit 19 indicates an impending leap second is inserted. Bit 20 indicates the start date and time. Bits 21-27 are BCD coded minutes. Bits 29-34 are BCD coded hours. Bits 36-41 are BCD encoded day of month Bits 42-44 are BCD weekday Bits 45-49 are BCD encoded encrypted year. Bits 50-57 are BCD coded years. Finally, a number of parity bits are inserted encoded data as follows. Parity bits to 28 bits 21-27. Parity bit 35-bit covers 29-34. Parity bit covers 58 bits 36-57.
To summarize, the DCF-77 transmission time is a reliable and accurate time from NTP server systems and applications, timing of other computers. The signal can be received in the vicinity of the NTP server same time, thus reducing installation costs. Furthermore, the right line before encoding the date of synchronization of the transmission allows the simple implementation of NTP server software. In fact, the standard distribution NTP server software drivers for Linux includes a reference clock for DCF-77.
Showing posts with label Decoding. Show all posts
Showing posts with label Decoding. Show all posts
Thursday, February 18, 2010
Sunday, February 14, 2010
Decoding the DCF-77 Radio Time Signal
The DCF-77 time of radio is used by the NTP server and PC systems to provide more accurate synchronization of time-critical applications. This article describes how the DCF-77 time signal is decoded by NTP server and computer systems to provide a precise reference time.
The DCF-77 time of the issuer.
The DCF-77 time signal is a long time short-wave radio antenna signal Mainflingen, near Frankfurt, Germany. The radio signal is maintained by T-Systems, a division Deuche Telecom, and has been in operation since 1959. The DCF-77 signal is generated by highly accurate atomic clocks located at the German National Physics Laboratory. When decoded, is a very specific reference to the timing and clock synchronization computer.
DCF-77 Time Code
Date and time information is transmitted continuously, repeated every minute. The data is transmitted as an amplitude modulated pulse width coded data signal. Each bit of data is transmitted as one pulse per second. The data is transmitted over time and the current date, leap second indicator, indicators of time, the identification of the issuer and the parity bit.
The duration of each pulse is decoded as follows: one mark for a second period of 100 milliseconds, is decoded as a binary zero, a second mark for a period of 200 milliseconds, is decoded as binary.
Of data transmitted.
Date and time information is presented in BCD (Binary Coded Decimal) format and is encoded as follows: 0-14 bits are not used, but can provide information on future state, bit 15 indicates that the use of backup transmitter, 16 bit (A1), said that the announcement of the change of time, 17-bit (Z1), said that summer is in use (EST) 18-bit (Z2), indicates the standard time (CET), 19 bits (A2), announces a leap second; Bit 20 indicates the start time information, bits 21-27, BCD encoded minutes and 28 bit (P1), the parity bit covers 21-bit 29-bit -27 -- BDC 34 time-coded, 35-bit (P2), the parity bit covers bits 29-34 bits 36-41, BCD encoded day of the month, bits 42-44, BCD encoded day of the week, bit 45-49, coded BCD months of the year, the bits 50-57, BCD encoded years, 58-bit (P3), parity bit covers the bit 36-57.
The DCF-77 data bits 1-14 are generally used by any algorithm, decodes and May to provide information on the status of future emissions. Z1 bit 'of time zone and Z2 indicate the current state of the economy days. When the time CET airs, Z1 and Z2 is equal to zero is for the moment CSTA is a Z1 and Z2 is equal to zero. The DST-bit ad 'of this change, A1, indicates an imminent change or HEC. The leap second announcement bit indicates the imminent introduction of a second jump. The three parity bits P1 to P3-complete information prior to an even number of ones (parity).
Examples
Received DCF-77 bit stream: 00000000000000000010100000000011010110000001001001000110011 once decoded and the date: Tuesday 01/12/1998 16:00
Received DCF-77 bit stream: 00000000000000000010110000001011010110000001001001000110011 once decoded and the date: Tuesday 01/12/1998 16:01
The DCF-77 time of the issuer.
The DCF-77 time signal is a long time short-wave radio antenna signal Mainflingen, near Frankfurt, Germany. The radio signal is maintained by T-Systems, a division Deuche Telecom, and has been in operation since 1959. The DCF-77 signal is generated by highly accurate atomic clocks located at the German National Physics Laboratory. When decoded, is a very specific reference to the timing and clock synchronization computer.
DCF-77 Time Code
Date and time information is transmitted continuously, repeated every minute. The data is transmitted as an amplitude modulated pulse width coded data signal. Each bit of data is transmitted as one pulse per second. The data is transmitted over time and the current date, leap second indicator, indicators of time, the identification of the issuer and the parity bit.
The duration of each pulse is decoded as follows: one mark for a second period of 100 milliseconds, is decoded as a binary zero, a second mark for a period of 200 milliseconds, is decoded as binary.
Of data transmitted.
Date and time information is presented in BCD (Binary Coded Decimal) format and is encoded as follows: 0-14 bits are not used, but can provide information on future state, bit 15 indicates that the use of backup transmitter, 16 bit (A1), said that the announcement of the change of time, 17-bit (Z1), said that summer is in use (EST) 18-bit (Z2), indicates the standard time (CET), 19 bits (A2), announces a leap second; Bit 20 indicates the start time information, bits 21-27, BCD encoded minutes and 28 bit (P1), the parity bit covers 21-bit 29-bit -27 -- BDC 34 time-coded, 35-bit (P2), the parity bit covers bits 29-34 bits 36-41, BCD encoded day of the month, bits 42-44, BCD encoded day of the week, bit 45-49, coded BCD months of the year, the bits 50-57, BCD encoded years, 58-bit (P3), parity bit covers the bit 36-57.
The DCF-77 data bits 1-14 are generally used by any algorithm, decodes and May to provide information on the status of future emissions. Z1 bit 'of time zone and Z2 indicate the current state of the economy days. When the time CET airs, Z1 and Z2 is equal to zero is for the moment CSTA is a Z1 and Z2 is equal to zero. The DST-bit ad 'of this change, A1, indicates an imminent change or HEC. The leap second announcement bit indicates the imminent introduction of a second jump. The three parity bits P1 to P3-complete information prior to an even number of ones (parity).
Examples
Received DCF-77 bit stream: 00000000000000000010100000000011010110000001001001000110011 once decoded and the date: Tuesday 01/12/1998 16:00
Received DCF-77 bit stream: 00000000000000000010110000001011010110000001001001000110011 once decoded and the date: Tuesday 01/12/1998 16:01
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