Decoding the DCF-77 Radio Time Signal

The DCF-77 radio time transmission is utilised by many NTP server and PC computer systems to provide accurate synchronisation of time critical applications. This article describes how the DCF-77 time signal is decoded by NTP server and computer systems to provide an accurate timing reference.

The DCF-77 Time Transmitter.

The DCF-77 time signal is a long-wave radio time signal broadcast from Mainflingen, near Frankfurt, Germany. The radio signal is maintained by T-Systems, a sub-division of Deuche Telecom, and has been in operation since 1959. The DCF-77 signal is generated from extremely accurate atomic clocks located at the German National Physics Laboratory. When decoded, it provides a highly accurate timing reference for clocks and computer timing equipment.

DCF-77 Time Code.

Time and date information is transmitted continuously, repeated each minute. The data is transmitted as an amplitude modulated, pulse-width coded data signal. Each data bit is transmitted as one pulse per second. The data transmitted consists of the current time and date, leap second indicator, daylight saving time indicator, transmitter identifier and parity bits.

The duration of each transmitted pulse is decoded as follows: a second mark with a duration of 100 milliseconds is decoded as a binary zero; a second mark with a duration of 200 milliseconds is decoded as a binary one.

Transmitted Data.

Time and date information is presented in BCD (Binary Coded Decimal) format and is encoded as follows: bits 0-14 are unused, but may provide future status information; bit 15 indicates use of backup transmitter; bit 16 (A1), indicates the announcement of daylight saving change; bit 17 (Z1), indicates daylight saving is in use (CEST); bit 18 (Z2), indicates standard time (CET); bit 19 (A2), announces a leap second; bit 20, indicates start of time information; bits 21-27, BCD encoded minutes; bit 28 (P1), parity bit covers bits 21-27; bits 29-34, BDC encoded hours; bit 35 (P2), parity bit covers bits 29-34; bits 36-41, BCD encoded day of month; bits 42-44, BCD encoded day of week; bits 45-49, BCD encoded month of the year; bits 50-57, BCD encoded year; bit 58 (P3), parity bit covers bits 36-57.

The DCF-77 data bits 1-14 are generally unused by any decoding algorithm and may provide status information in future broadcasts. The time zone bits Z1 and Z2 indicate current daylight saving time status. When CET time is being broadcast, Z1 is zero and Z2 is one, for CEST time, Z1 is one and Z2 is zero. The daylight saving change announcement bit, A1, indicates an imminent change to or from CET. The leap second announcement bit indicates the imminent insertion of a leap second. The three parity bits P1-P3 compliment the preceding information to an even number of ones (even parity).

Examples:

Received DCF-77 bit stream: 00000000000000000010100000000011010110000001001001000110011 Decoded time and date: Tuesday 01/12/1998 16:00

Received DCF-77 bit stream: 00000000000000000010110000001011010110000001001001000110011 Decoded time and date: Tuesday 01/12/1998 16:01

Biography:
Dave Evans develops NTP Server synchronisation systems to ensure accurate time on PC�s and computer networks. Dave has been involved in the development of dedicated NTP server systems, NTP synchronised digital wall clock systems and atomic clock time synchronisation products. Click here to find out more about SNTP and DCF-77 NTP Server Systems.

– dave evans

A Purchase Guide to Budget Notebooks

Since it became commercially available back in the early eighties, notebooks called the attention of computer users because of its small size and portability. Not much of a commercial success back then, it only took a short time before the computer industry improved this item, up to a point that is now considered to be one of the best selling computer consumer products.

For one who intends to buy a budget notebook, he may have some difficulties in picking the right one, since there are several notebook manufactures offering so many models. Budget notebooks are in a class by itself with basic features but capable of delivering full solutions for computer related tasks.

For an easy guide to budget notebooks, check the following major manufactures:

SONY

Sony VAIO notebooks are fashioned products targeted to consumers who demand flexibility and power without compromise. It is expected to find features such as 15.4“ WXGA, duo core processor and 100 gb hard disk. Although not the cheapest of budget notebooks, it compensates the higher price by offering more technological features.

Most common features one can expect from Sony budget notebooks: 1 – Intel Core Duo Processor T2250 1.72 Ghz; 2 – Windows Vista; 3 – 1 gb DDR2 ram; 4 – Widescreen XGA display type; 5 – Intel graphics media accelerator 950; 6 – 100 gb SATA hard disk 5400 rpm; 7 – CD-RW/DVD rom; 8 – wireless lan 802.11 a/b/g; 9 – Modem and Lan port 10/100; 10 – USB connectivity; 11 – It weighs around 6.5 pounds; 12 – Lithium ion battery up to 5.5 hours; 13 – One year limited warranty. Price starts from U$ 929.00 and up according with optional accessories.

DELL

With features such as 15.4“ WXGA, duo core processor and ATI Radeon Xpress graphics, Dell budget notebooks offer a flexible combination of power, mobile productivity and entertainment at a good price.

Most common features one can expect out of these notebooks are: 1 – AMD Turion 62 X2 1.8 ghz/1mb cache processor; 2 – Windows Vista; 3 – 512 mb ram; 4 – Widescreen XGA display type; 5 – ATI Radeon Xpress 256 mb video graphics chipset; 6 – Up to 80 gb hard disk; 7 – CD-RW/DVD rom; 8 – It weighs around 6 pounds; 9 – 9-cell lithium ion battery; 10 – One year limited warranty. Price starts from U$ 549.00 and up according with optional accessories.

TOSHIBA

All Toshiba budget notebooks feature an 15.4“ diagonal WXGA display, DVD optical drive which reads and writes up to 11 formats, high speed wireless lan (802.11 b/g) for easy connection in networks.

Most common features one can expect out of these notebooks are: 1 – Intel Celeron processor with 1+ Ghz; 2 – Windows Vista; 3 – 512 mb ram; 4 – Widescreen XGA display type; 5 – Radeon Xpress 200M video graphics chipset; 6 – 60 gb hard disk; 7 – CD-RW/DVD rom; 8 – wireless lan but no Bluetooth connectivity; 9 – Modem and Lan port 10/100 mbps; 10 – USB and firewire connectivity; 11 – It weighs around 5 pounds; 12 – 4-cell lithium ion battery; 13 – Tv-out s-video; 14 – One year parts and labor warranty. Price starts from U$ 599.00 and up according with optional accessories.

HP

HP Budget notebooks with features such as 15.4“ display screen, AMD Sempron 3500+ and a sophisticated black resin finish, offer an attractive mix of style, mobility and performance.

Expected features one can find in this HP notebook category: 1 – AMD Sempron 3500+; 2 – Windows Vista; 3 – 15.4“ WXGA Widescreen; 3 – 512 mb ddr2; 4 – CD-RW/DVD rom; 4 – Wireless connectivity 802.11b/g wlan; 5 – It weighs around 7 pounds; 6 – Nvidia video graphics chipset with 256 mb; 7 – 6-cell lithium ion battery; 8 – USB, lan and modem port; 9 – Integrated stereo speakers; 10 – 60 gb SATA hard disk; 11 – Tv-out s-video; 12 – One year warranty in parts and labor. Price starts from U$ 569.00 and up according with optional accessories.

A while ago portable electronics devices were a luxury at an expensive price. Nowadays it became an affordable must have kind of product for lots of people. Notebooks are in this category for sure! And basic notebooks are the best option for those who are in a tight budget. So, if portability is a must for your personal or professional computer related tasks, waste no more time. Get yourself a budget notebook!

– polomercantil.com –

Notebook Buying Tips

Why notebook became so popular? It has been estimated that notebook sales has increased an average of 20% per year in the United States alone. Among the many advantages it offers, portability is one of the main reason people end up making a purchase of it. However before any purchase is made, other features should be considered as well.

Notebook was first made available in the early eighties. Although much heavier and bulkier than today’s notebooks, it had the unique portability feature that put this innovative product in a class by itself. Although not much of a commercial success then, it gave the computer industry a goal to pursue in manufacturing this item with better weight, size and performance ratio and making one of today’s most wanted computer hardware.

Notebook size has got much smaller, however big enough to make one feel very comfortable in handling and operating computer related tasks. One can find it in sizes best categorized as: 1 – Tablet PC has the size of paper tablet and weighs no more than 4 pounds; 2 – Ultra Portable is a little bigger than Tablet Pc and weighs around 4 pounds, no internal CD or DVD drive, display of 12 inches or smaller; 3 – Thin and Light is a mid-size notebook, 10-14″ x 10″, 1 to 1.5 thick, and weighs around 7 pounds, wireless network capability, 14-inch displays, combo CD-RW/DVD; 4 – Desktop replacement is the largest category of notebooks, more than 12 x 10″ and weighs more than 7 pounds, 15-17 inches displays or larger, wireless network capability, combo CD-RW/DV.

Also an important feature one should look for is performance. Notebooks provide very close performance in comparison with traditional desktop computers, and should handle all computer related tasks with great ease. Whenever purchasing a notebook, make sure it has the latest cpu model, large ram memory and hard disk space. Notebook performance is directly related with cpu clock, ram memory and hard disk space. For these items, big is never enough.

Another feature one should look for is the dvd player. It can come in handy for entertainment purposes, enabling one to watch movies while traveling. Wireless connection is also a feature to look for in a notebook. Some notebooks feature an infrared port, which can be used to connect a mobile phone. Also there are other wireless technologies such as Bluetooth and Wi-Fi, which allows mobile phone, printers and PDA to be connected at certified public and private network. The ability to have a mobile connection is definitely a plus in today’s connected world.

Expansion capability for notebooks can be done thru the use of plug-in pc cards. Although there is a new standard called ExpressCard, which is smaller and faster plug-in card that provides more features for multimedia tasks.

Notebooks have certainly become an item required for one’s mobile computer related tasks, whether it is used for public, private, personal or professional purposes. Its portability and small size make an attractive all around computer hardware item. For those looking for mobile computer hardware, notebooks can certainly become a good solution at affordable prices.

– polomercantil.com –