Editor's note: The following information is provided as an aid in developing timecode software for primary time servers using various national standards dissemination media. No claim is made on correctness other than by the authors listed. Information included in this version applies to DCF77 (Germany), MSF (United Kingdom), TDF (France) and WWV (United States). David L. Mills 5 January 1990 Time and Standard Frequency Station DCF77 (Germany) (Original in German available from the address below. Translation errors courtesy of Peter Lamb, Swiss Fed. Inst. of Technology). Physikalisch-Technische Bundesanstalt (PTB) Braunschweig, Febuar 1984 Lab 1.21 Bundesalle 100 D-3300 Braunschweig Legal basis and responsibility for the transmissions from DCF77 The 1978 law on time standards defines legal time in Germany on the basis of Coordinated World Time (UTC) and gives the PTB responsibility for the keeping and broadcasting of legal time. As well as this, the time standards law empowers the Federal government to issue regulations for the introduction of Summer Time. Legal time in the FRG is either Middle European Time (MEZ - German abbreviation) or, in case of its introduction Middle European Summer Time (MESZ). The following relationships hold between UTC and MEZ and MESZ. MEZ(D) = UTC(PTB) + 1h MESZ(D) = UTC(PTB) + 2h Legal time is generated in the PTB Atomic Clock Building in Braunschweig and it is broadcast mainly through the LF transmitter DCF77 which the PTB rents from the German Post Office (DBP). The PTB has sole responsibility for the control of DCF77, while the DBP has responsibility for the transmitter and antennas. Queries should be directed to the above address or by telephone to 0531/592 1212 or 0531/592 1210, or by telex to 952822 ptb d. DCF77 Specifications Location: Mainflingen transmitter complex, (50:01N, 09:00E), about 25km south-east of Frankfurt a. Main. Carrier Frequency: Standard frequency 77.5kHZ, derived from the PTB atomic clocks. Relative deviation of the carrier from specifications: averaged over 1d: <1e-12 averaged over 100d: <2e-13 The carrier phase is controlled so that deviations relative to UTC(PTB) are never greater than +-0.3us. Larger phase and frequency variation observed at the receiver are due to summation of ground and space waves. Power output: Transmitter power 50kw, estimated emitted power approx. 25kW. Antenna: 150m high (backup antenna 200m high) vertical omnidirectional antenna with top capacitance. Transmission times: 24-hour continuous service. Short interruptions (of a few minutes) are possible if, because of technical problems or servicing,, the service must be switched to a backup transmitter or antenna. Thunderstorms can cause longer interruptions to the service. Time signal: The carrier is amplitude-modulated with second marks. At the beginning of each second (with the exception of the 59th second of each minute), the carrier amplitude is reduced to 25% for the duration of either 0.1 or 0.2 seconds. The start of the carrier reduction marks the precise beginning of the second. The minute is marked by the absence of the previous second mark. The second marks are phase-synchronous with the carrier. There is a relatively large uncertainty possible in the time of the second mark which depends on the receiver position. The causes are the relatively low bandwidth of the antenna, space wave and other interference sources. Despite this, it is possible to achieve accuracy better than 1ms at distances of several hundred kilometers. Time code: The transmission of the numerical values for minute, hour, day, weekday, month and year are BCD-encoded through the pulse duration modulation of the second marks. A second mark with duration 0.1s encodes a binary 0 and a duration of 0.1s encodes 1. The order of encoding is shown in the following diagram [replaced by a table in this translation]. The three test bits P1, P2 and P3 extend the 3 major sections of the time code (7 bits for minutes, 6 bits for the hour and 22 bits for the date, including the week day number) to maintain an even count of 1's. The second marks No. 17 and 18 indicate the time system for the transmitted time codes. In the case of transmission of MEZ, mark 18 has a duration of 0.2s and mark 17 a duration of 0.1s. If MESZ is being transmitted, this is reversed. Furthermore, an approaching transition from MEZ to MESZ or back is announced by extending mark 16 from 0.1 to 0.2s for one hour prior to the changeover. Encoding Scheme [diagram in original] Mark number(s) Encodes (01.s=0, 0.2s=1) 0 Minute, always 0 (0.1s) 1-14 Reserved 15 0=Normal antenna, 1=backup antenna 16 1=Approaching change from MEZ to MESZ or back 17,18 Time zone 0,1=MEZ; 1,0=MESZ 19 The leap second is encoded in this bit one hour prior to occurrence. 20 Start bit for encoded time, always 1 21-27 1, 2, 4, 8, 10, 20, 40 Minutes (mark 21=1 minute) 28 P1 maintains even parity for marks 21-28 29-34 1,2,4,8,10,20 Hours (mark 29=1 hour) 35 P2 maintains even parity for marks 29-35 36-41 Day in month (1, 2, 4, 8, 10, 20) 42-44 Day in week (1,2,4) 45-49 Month number (1, 2, 4, 8, 10) 50-57 Year (1, 2, 4, 8, 10, 20, 40, 80) 58 P3 maintains even parity for marks 36-58 There is no mark transmitted for the 59th second. Literature P. Hetzel, "Die Zeitsignal- und Normalfrequenzaussendungen der PTB ueber den Sender DCF77: Stand 1982" [The PTB time signal and standard frequency transmissions from DCF77: Status 1982] in "Funkuhren" [Radio clocks], W. Hilberg, Oldenburg Publishers, Munich & Vienna 1983, pp 42- 57. G Becker & P. Hetzel, "Vortraege ueber DCF77" [Lectures: DCF77], PTB Reports, PTB-Me-23 (1979), pp 185-253. Braunschweig 1984 Additional information: DCF77 Since July 1983, the DCF77 carrier has been phase modulated in a test configuration. The phase modulation is a pseudorandom binary sequence sent twice each second. The clock frequency of the binary sequence is 645.833...Hz and the phase shift \Delta\tau about 3% of the period (\^{=} 10\deg). Equal numbers of shifts of +\Delta\tau and -\Delta\tau are always sent, so that the mean frequency remains unchanged, and the use of DCF77 as a frequency standard is unaffected. The timecode is encoded in the sequence by inverting the sequence or not. Not inverted sequence corresponds to a 0 bit. The sequence is alleged to be generated by a 9 bit shift register which is coupled back on positions 5 and 9. The polynomial might be: x^9 + x^4 + 1. Because the pseudo-random bitstring has a strictly deterministic nature, the correlation analysis at the receiver end leads to a correlation function with triangular form, and thereby to timing information. Early test results show that the time information received with the help of pseudo-random phase modulation is more resistant to interference and more accurate (standard deviation \approx 10\mu s during the day and \approx 25\mu s at night) than the conventional method using amplitude modulated second marks. Since this new modulation method is compatible with previous usage of DCF77, and that the users have made no difficulties known to us, the tests have been extended. The transmission of the pseudo-random phase distortion still has experimental status, and should not be seen as a permanent commitment. Further information will be made available in the future. Announcement bit for a leap second The DCF77 control unit is currently being modified so that in future an announcement bit for a leap second can be sent. It is expected that for the first time on 1st July 1985 the second mark Nr. 19 will be extended to a length of 0.2s for one hour prior to the introduction of a leap second. Intelligent receivers will then be able to recognise the discontinuity and maintain correct indicated time in spite of a 61s minute. Availability The clock was made by a local radio amateur. Empfangsanlage DCF77 (SFr 690. complete, also available in kit form) Walter Schmidt Eichwisrain 14 8634 Hombrechtikon Switzerland LF reciever and decoder for the German time standard DCF77. As yet untested. Has a 1s impulse output driven direct from the reciever, which could be used in a similar manner to the pulse output on the Spectracom. Internal crystal-controlled clock reset each minute by the DCF77 minute mark. Indication available to program of whether currently synchronised, and a count of how long since the last synchronisation is available if running unsynchronised. Returns time with resolution 0.1s, but probably synchronised to the time of command reception, and not to the 0.1s counter. I will try to get the firmware changed if this is the case. Time and Frequency Station MSF (United Kingdom) Information entered by Philip Gladstone, extracted from a document issued by Rugby (VLF) Radio Station. Technical Details Service MSF 60 KHz Radiated Power 16 KW Schedule 24 hour (off for maintenance 1000-1400 GMT on the first Tuesday of the month) Duration of time signal emission Continuous Time signal modulation A1 Negative 100mS at the second, 500mS at the minute Epoch at Carrier Fall Carrier Frequency Stability +/- 3 in 10^12 Time Signal Accuracy 0.1mS relative UTC The Rubgy Frequency Standards Three Hewlett Packard sources are used -- one type 5061A Caesium Beam,and two type 5065A rubidium vapour -- and are installed in acontrolled-environment cubicle together with an AUSTRON type 2055 microstepper. This last is a precision rate adjuster which is used to vary the frequency of the Caesium standard to cater for the minute differences (of order parts in 10^12) which exist between all Caesium standards. This results in a 5MHz output from a crystal oscillator which is part of the feedback system. The 60KHz carrier is derived from this 5MHz by a digital tripler consisting of three positive edge detectors on a delay line using the propagation delay in integrated circuit inverters to produce three pulses seperated by 66.6 nanoseconds in each 200nS cycle of 5MHz. The resulting 15 MHz is then divided by 250 to obtain a square wave at 60 KHz. 100 KHz outputs are used to drive the digital clocks -- three Venner TSA 5586 clocks which give parallel BCD time output. These clocks are set an arbitrary 100 microseconds ahead of UTC (Rugby) to cater for the unavoidable delays in drive generators and transmitters. Time Stability 1. UTC (Rugby) is compared with UTC (NPL) by measurements at both sites relative to a readily identifiable edge in the field sync pulse train of the BBC TV transmission from Sandy Heath 2. UTC (NPL) is compared with UTC (BIH) by similar observations of a specified feature in the transmission from Sylt (7970-W) in the LORAN 'C' Norwegian Sea chain. 3. Rugby then use results supplied by BIH and NPL to calculate a direct comparison between UTC at Rugby and BIH. It should be noted that UTC (BIH) is a calculated 'paper' clock with no physical existence of its own and actually derived from the average of 30 or so standard clocks throughout the world. UTC (Rugby) is currently maintained within 4 parts in 10^13 of agreement with UTC (BIH), a comfortable margin over the claimed stability of 3 in 10^12. Why called MSF? It is a callsign like 2LO and GBR and while SF was the obvious acronym for Standard Frequency a three letter callsign could only begin with 2, G or M, the prefixes allocated to the UK by international agreement for station identification. M was available for use with the letters SF, G was not, so there was really very little choice in the matter. Pulse Train The Minute epoch is marked by a 500 mS break in the carrier. Actually, there is data transmitted in this gap, but very few people use it. There are four other types of signal that can be sent on the second. ______ _______________ | | | | Zero (normal marker) |_____| ______ _______________ | | | | One (Time, date, identifier) |__________| ______ _______________ | | | | Identifier one plus Parity or |_______________| BST one ______ ____ _______________ | | | | | | | | DUT1 one |_____| |____| ^ ^ ^ ^ | | | 300 ms | | 200 ms | 100 ms 0 (Second Epoch) Second 0 500ms break (100 Hz code) 1-8 Positive DUT1 (use either Zero or DUT1) 9-16 Negative DUT1 (use either Zero or DUT1) 17-24 Year (80,40,20,10,8,4,2,1) (Use Zero or One) 25-29 Month (10,8,4,2,1) (Use Zero or One) 30-35 Day (20,10,8,4,2,1) (Use Zero or One) 36-38 Day of Week (4,2,1) (Use Zero or One) 39-44 Hour (20,10,8,4,2,1) (Use Zero or One) (Localtime) 45-51 Minute (40,20,10,8,4,2,1) (Use Zero or One) 52 Zero 53 BST/UTC Change next hour (Use One or Ident) 54 Parity (over 17-24) (Use One or Ident) 55 Parity (over 25-35) (Use One or Ident) 56 Parity (over 36-38) (Use One or Ident) 57 Parity (over 39-51) (Use One or Ident) 58 BST (Use One or Ident) 59 Zero Notes 1. The 1Hz data applies to the following minute 2. When BST is in force, bit 58 is 300 mS and Data is 61 minutes fast of UTC. Bit 53 is 300 mS for the hour preceeding (0100 UTC) changes to and from BST. 3. Day 0 is Sunday 4. Parity sense is Odd. 5. The first 'n' bits in the DUT1 code being DUT1 (rather than Zero) indicates 0.'n' positive or negative DUT1. DUT1 is set up on switches to instructions via the Royal Greenwich Observatory, changes occurring approximately every five weeks. GMT is Greenwich Mean Time -- this is really UTC BST is British Summer Timer which is one hour ahead of GMT. Details of this can be obtained from Division of Electrical Science National Physical Laboratory Queens Road Teddington Middlesex TW11 0LW United Kingdom Decoding Clocks A number of clocks are available in the UK, ranging from wall clocks at around 100 UKP to digital computer clocks at 1000-2000 UKP. Hobbyist kits are also available at around 20 UKP that provide the raw 1 Hz data. Time and Standard Frequency Station TDF (France) Provided courtesy of Richard B. Langley, University of New Brunswick Station: TDF, Allouis, France Address: Centre National d'Etudes des Telecommunications PAB - STC - Etalons de frequence et de temps 196 avenue Henri Ravera F - 92220 Bagneux France Coordinates: 47d 10' N, 2d 12' E Frequency: 162 kHz Power: 2,000 kW Schedule: continuous except every Tuesday from 01:00 to 05:00 UTC Form of Time Signals: TDF is an amplitude modulated longwave broadcasting station, transmitting the programs of the France-Inter Network of Telediffusion de France (TDF). Time signals are transmitted by phase modulation of the carrier by + and -1 radian in 0.1 s every second except the 59th second of each minute. This modulation is doubled to indicate binary 1. The numbers of the minute, hour, day of the month, day of the week, month and year are transmitted each minute from the 21st to the 58th second, in accordance with the French legal time scale. In addition, a binary 1 at the 17th second indicates that the local time is 2 hours ahead of UTC (i.e., summer time), a binary 1 at the 18th second indicates when the local time is 1 hour ahead of UTC (i.e., winter time). A binary 1 at the 14th second indicates that the current day is a public holiday (14 July, Christmas, etc.) and a binary 1 at the 13th second indicates that the current day is the day before a public holiday. Relative Uncertainty of the Carrier Frequency: 2 parts in 10^12. Radio Clocks Available: Horloge 59 HF BHL Electronique Zone Industrielle B.P. 8 F - 14540 Bourguebus France Recepteur horaire sur France-Inter G-O Dyna Electronique 36 avenue Gambetta F - 75980 Paris Cedex 20 France RTD 101 telematique SA Zirst-chemin des pres F - 38240 Meylan France Information Sources: Annual Report of the BIPM Time Section for 1989, Bureau International des Poids et Mesures, Pavillon de Breteuil, F - 92312 Sevres Cedex, France. Zeitzeichensender / Time Signal Stations (bilingual: German and English) by Gerd Klawitter, Siebel Verlag, Bonhoeffer Weg 16, D-5309 Meckenheim, Germany. Time and Frequency Stations WWV/WWVH (United States) Editor's note: This information consists of a RFP issued for timecode generators to replace aging equipment used at stations WWV/WWVH for the last twenty years. Certain features of the new timecode format may not match the equipment currently installed. Attachment 1 to Department of Commerce Solicitation number 52RANB00C059, issued 1-23-90 Retyped by Bob Clements, K1BC, clements@bbn.com Page 1 of 15 Revised 11/22/89 SPECIFICATIONS TIME CODE GENERATOR/PROGRAMMER 1.0 Scope This specification establishes the requirements for two time code generator/programmer systems that will be used to generate precision timing signals for use by NIST standard time and frequency stations WWV and WWVH. Each of these systems will consist of: (1) Three (3) time code generator/programmer units, and (2) Software and interfacing hardware to provide for entering commands to the time code generators through a computer. 2.0 Performance Requirements 2.1 General The time code generator shall produce precision timing signals in the forms and formats specified in a later section of this specification. A front panel display of generated time shall be incorporated in the equipment. In the equipment design and construction, emphasis shall be placed upon the use of proven techniques and the maximum use of reliable solid-state components and circuitry. It is the intent of this specification to define equipment reflecting the current state-of-the-art with a proven record of reliability in field operation. 2.2 Function The time code generator shall contain all the necessary circuitry to generate serial and parallel time code signals and to synchronize generated time with a reference time signal. It shall also contain circuitry for the generation of voice time announcements and for multiplexing internally generated audio with audio supplied from external sources. 2.3 Input Signals 2.3.1 General The unit shall accept various input signals from external sources. All inputs shall be via connectors located on rear of unit. Page 2 of 15 2.3.2 Inputs (1) The unit shall accept a 5 MHz sinusoidal signal from an external frequency standard as the source of the time base frequency. System shall be adequately filtered to prevent miscount due to transient pulses, line surges, or power failure. The input signal range shall be from 0.5 to 2 volts RMS. All generated tones, codes, gates, time pulses, etc., shall be electronically derived from this 5 MHz signal. Input impedance shall be at least 200 ohms resistive. This input shall be via a BNC connector. (2) The unit shall accept audio inputs on 16 channels via a 32 pin ribbon connector with signal conductor and ground for each channel. Nominal input audio level is 1 volt RMS. Each channel audio level shall be independantly adjustable. Input impedance for each channel shall be 5000 ohms. (3) RS-232C serial communications a. 9-pin male connector, IBM standard b. RS-232C line driver, +/- 15 volts c. All lines active to allow connection of a modem d. Parallel operation with one ribbon cable for multiple code generators is allowed 2.4 Output Signals 2.4.1 General The unit shall provide the following output signals, all (except external audio) derived from the standard 5MHz input. All output signals to work into a 50 ohm load unless otherwise noted. Output signals to be via connectors located on rear of unit unless otherwise specified. 2.4.2 Outputs (1) Composite audio output The unit shall provide a composite audio output, identical at each of four jacks. a. 4 silver-plated BNC connectors b. 3 volts peak-to-peak (adjustable 20%) maximum level of the composite audio signal c. Enough drive for 1 volt RMS into 50 ohm load for each of 4 outputs, with each output fully independent of the others Page 3 of 15 This output provides the modulation signal for the WWV/WWVH transmitters. Its composition is described elsewhere in this specification. (2) 1 PPS sync output a. Two silver-plated BNC connectors, one on front panel, one on back b. 20 us pulse with < .1 us rise time, able to drive terminated 50 ohm coax from either or both connectors, with 5 volts peak-to-peak amplitude (3) Comparator output To mate with the existing comparator, this output shall be as follows: a. Amphenol 57-40360 connector b. 36 pins as follows: 1,19 - no connection 2,20 - no connection 3,21 - no connection 4,22 - no connection 5,23 - no connection 6,24 - no connection 7,25 - no connection 8,26 - no connection 9,27 - no connection 10,28 - IRIG H DC level shift code, TTL line driver into twisted pair 11,29 - 1 KHz / 1.2 KHz square wave, TTL line driver into twisted pair 12,30 - no connection 13,31 - no connection 14,32 - no connection 15,33 - no connection 16,34 - no connection 17,35 - no connection 18,36 - no connection (4) IRIG H DC Level Shift Code This output, which appears on pins 10 and 28 of the Comparator Output, shall also be available at a back- panel BNC connector. Page 4 of 15 (5) External Audio Channel Trigger Outputs a. 32 pin ribbon connector, with trigger and ground for each channel b. Enough drive for >10 volts into 5K ohm load, with a maximum output voltage of 15 volts c. When this trigger is present on a particular channel during its assigned minute, it shall appear as a pedestal lasting from 0 seconds through the 44th second of that minute. (45 seconds total length) 2.5 Generated tones The unit shall generate audio tones of several frequencies and shall provide appropriate gates and logic to pass these to the composite audio output during certain time intervals as described below. 2.5.1 General All tones are zero phase positive-going at start of each second, harmonic distortion < -50dB, noise and non-harmonic distortion < -60dB 2.5.2 Marker tones - 100% modulation (1) First of each hour : 1500 Hz for 800 ms (2) First of each minute: 1000 Hz for 800 ms - WWV 1200 Hz for 800 ms - WWVH (3) First of each second: 1000 Hz for 5 ms - WWV 1200 Hz for 5 ms - WWVH (4) Skip seconds 29 and 59 (5) UT1 correction: add additional 1000/1200 Hz for 5 ms beginning 100 ms after the start of the seconds marker. This creates a "doubled" tick. Plus correction: seconds 1-8 (example +.3 addas at 1,2, and 3 seconds) Minus correction: seconds 9-16 (example -.4 adds at 9,10,11, and 12) 2.5.3 Steady tones - 50% modulation (1) Choice of no tone, 440 Hz, 500 Hz, 600 Hz according to minute and station (see hourly code table) (2) Tone starts at 1.030 seconds into the minute and ends at 44.990 seconds Page 5 of 15 (3) Tone is suppressed from -.010 to +.030 seconds, relative to the start of each second that has a "tick" (4) Tone is suppressed for 5 ms during additional UT1 correction "tick" (5) Valid data ranges are: seconds: 00 to 59 (not explicitly transmitted) minutes: 00 to 59 hours : 00 to 23 day : 001 to 366 year : 00 to 99 UT1 : .0 to .7 plus sign bit Note: "Low" subcarrier shall be adjustable from 0% to 20% of the peak value of the 100-Hz code. 2.5.5 Time Code Generator - Hourly Format Table Note: This information is supplied for clarification purposes only. Minute WWV WWVH 00 station ID no tone 01 600 Hz 440 Hz * 02 440 Hz * 600 Hz 03 600 Hz 500 Hz / reserved 04 500 Hz / reserved 600 Hz 05 600 Hz 500 Hz 06 500 Hz 600 Hz 07 600 Hz 500 Hz 08 storm info no tone 09 storm info no tone 10 storm info no tone 11 600 Hz / storm info no tone 12 500 Hz 600 Hz 13 600 Hz 500 Hz [* 440 Hz replaced by "no tone" during hour 0 of each UTC day] Page 6 of 15 14 500 Hz 600 Hz 15 600 Hz no tone 16 Omega reports no tone 17 600 Hz no tone 18 Geoalerts no tone 19 600 Hz no tone 20 500 Hz 600 Hz 21 600 Hz 500 Hz 22 500 Hz 600 Hz 23 600 Hz 500 Hz 24 500 Hz 600 Hz 25 600 Hz 500 Hz 26 500 Hz 600 Hz 27 600 Hz 500 Hz 28 500 Hz 600 Hz 29 no tone station ID 30 station ID no tone 31 600 Hz 500 Hz 32 500 Hz 600 Hz 33 600 Hz 500 Hz 34 500 Hz 600 Hz 35 600 Hz 500 Hz 36 500 Hz 600 Hz 37 600 Hz 500 Hz 38 500 Hz 600 Hz 39 600 Hz 500 Hz 40 500 Hz 600 Hz 41 600 Hz 500 Hz 42 500 Hz 600 Hz 43 600 Hz 500 Hz 44 500 Hz 600 Hz 45 no tone Geoalerts 46 no tone 600 Hz 47 no tone Omega reports 48 no tone storm info 49 no tone storm info 50 no tone storm info 51 no tone storm info 52 no tone 600 Hz / storm info 53 600 Hz 500 Hz 54 500 Hz 600 Hz 55 600 Hz 500 Hz 56 500 Hz 600 Hz 57 600 Hz 500 Hz 58 500 Hz 600 Hz 59 no tone station ID 2.5.6 Time Code Generator - BCD Format Table Second Data 00 low subcarrier 01 0 02 0 Page 7 of 15 03 0 04 0 05 0 06 0 07 0 08 0 09 position marker 1 10 minute 1 11 minute 2 12 minute 4 13 minute 8 14 0 15 minute 10 16 minute 20 17 minute 40 18 0 19 position marker 2 20 hour 1 21 hour 2 22 hour 4 23 hour 8 24 0 25 hour 10 26 hour 20 27 0 28 0 29 position marker 3 30 day 1 31 day 2 32 day 4 33 day 8 34 0 35 day 10 36 day 20 37 day 40 38 day 80 39 position marker 4 40 day 100 41 day 200 42 0 43 (new) leap second warning 44 (new) Daylight Saving Time indicator #2 45 (new) year 1 46 (new) year 2 47 (new) year 4 48 (new) year 8 49 position marker 5 50 UT1 sign 51 (new) year 10 52 (new) year 20 53 (new) year 40 54 (new) year 80 55 Daylight Saving Time indicator #1 56 UT1 .1 Page 8 of 15 57 UT1 .2 58 UT1 .4 59 position marker 0 Note: Daylight Saving Time indicator bits #1 and #2 are scheduled for change by the operator. The normal procedure is for DST indicator bit #1 to change at 0000 UTC on the day of a change to or from Daylight Saving Time and DST indicator bit #2 to change in the same way 24 hours later at 0000 UTC on the day after the time change. When both bits are set to "0", standard time is in effect and it is not a day of time change; when both bits are set to "1", Daylight Saving Time is in effect and it is not a day of time change. Each receiver can then interpret these bits unambiguously so as to change onto or off of Daylight Saving Time at 2:00 AM receiver local time. Note: Leap seconds are always inserted/deleted at the last second of the UTC month. Leap second warning is scheduled to be turned on at any time during the month to which a leap second is being added, and is automatically turned off immediately after the leap second. The UT1 bits also automatically change after a leap second. Incremental UT1 changes may be scheduled by the operator at any time. 2.6 Voice Modulation 2.6.1 General The highest amplitude spectral component shall be > 2.25 volts peak-to-peak. The generated audio spectrum shall be from 50 Hz to 5 KHz. All voice modulation is suppressed as follows: 1040 ms interval (-0.010 s to +1.030 s) for hour and minute marker tones 40 ms interval (-0.010 s to +0.030 s for second marker "tick" 5 ms interval (+0.100 s to +0.105 s relative to start of doubled UT1 "ticks" All internally generated voice announcements must be of broadcast quality. 2.6.2 Voice Time Announcement, once per minute (1) The internally generated voice time announcements should consist of appropriate words and phrases which have been digitized and stored in ROM chips within the time code generators. Professional announcers (male for WWV; female for WWVH) should be used as the sources for these digitized recordings in ROM. The digitizing and other related processes must provide broadcast-quality in the output announcements. Page 9 of 15 (2) Message content: Example of a typical time announcement: "At the tone, 17 hours, 23 minutes, Coordinated Universal Time." (3) Timing of broadcast announcements: WWVH: WWVH time announcements to end 51 +/- 0.1 seconds after each minute WWV: WWV time announcements to end 58 +/- 0.1 seconds after each minute The duration of each announcement should be such that no overlap occurs between the WWVH and WWV announcements. 2.6.3 Voice messages from external sources - see hourly format table. (1) 45 second recording from external source, starting on the minute (2) 16 audio channels, each with trigger output and multiplexed input, with fully programmable channel vs. minute selection (3) One or two of the 16 channels will be used for the twice-per-hour station ID announcements. These announcements begin at 1.030 s after the start of the 00th and 30th minutes for WWV and the 29th and 59th minutes for WWVH. The station ID announcements will be provided to the time code generators from external, NIST-owned digital recording equipment. (4) Only one channel active at any one time (5) Same channel may be repeated for different minutes 2.7 Controls 2.7.1 General As many of the operating controls as is practical shall be digital commands, entered into non-volatile memory in the time code generator via RS-232 link from an existing computer. The software must be compatible with an MS-DOS operating system. 2.7.2 Time Synchronization (1) Methods shall be provided to start and stop time accumulation and to independently reset time of day, day of year, and year to any desired value. (2) Controls or commands shall be provided to adjust the time position of the 1 pps pulse with respect to an external Page 10 of 15 reference signal. Time shall be adjustable to within 0.1 us. Note: All internally generated tones and codes must remain keyed to the leading edge of the 1 pps pulse. 2.7.3 Programmed Controls (1) Programmable table for each minute in the hour, with choices: a. No tone, 440 Hz, 500 Hz, or 600 Hz b. External audio channel (total of 16 external channels). (2) Programmable table for each second in the minute, BCD tone choices: a. Second 00 shall have a fixed (non-programmable) low tone b. Seconds 09, 19, 29, 39, 49, and 59 shall have a fixed position marker c. Seconds 10-13, 15-17, 20-23, 25-26, 30-33, 35-38, 40-41, 45-48, and 51-54 shall have either a binary zero or a binary one signal, controlled by the time code generator depending on the generated time. (The operator may set the time initially, which is then used to control the bits, but he does not have programmable control of the bits individually.) d. Seconds 43-44, 50, and 55-58 have specifically defined information functions and are to be programmable by the operator in setting those functions. However, they shall not be individually randomly accessible for programming. e. Seconds 1-8, 14, 18, 24, 27-28, 34 and 42 shall be individually programmable by the operator as either a binary zero or a binary one, but shall have a default value of zero. (3) Fully automatic Daylight Saving Time, leap second, and DUT1 operation, with dates programmable ahead of time by operator. Provision shall also be included for manually setting these indicator bits to desired values when the values are to be effective immediately. (4) Program commands - over RS-232 serial link (menu driven) (5) Each unit is addressable over the common RS-232 bus. Any command may be sent to any unit. Where applicable, a single command may be sent simultaneously to all units Page 11 of 15 at the option of the operator. The software and hardware must, as a minimum, allow the operator to perform the following functions: a. Set time, date, and year to nearest second b. Adjust time to nearest 0.1 microsecond c. Read and update hour format table, assign audio channels to minutes d. Read and update BCD format table e. Schedule date for next Daylight Saving Time change f. Schedule date for next DUT1 correction change g. Schedule date for next leap-second insertion h. Set WWV or WWVH tone frequencies, time announcements i. Facilitate unit-to-unit time comparisons by providing a software menu option for displaying time readings (to nearest second) for all time code generators on the same screen j. Facilitate unit-to-unit format-table comparisons by providing a software menu option for displaying format information from all time code generators on the same screen 2.8 Front Panel Description (1) LED display of year, day, hour, minute, second, DUT1 correction (2) Thumbwheel entry of standard channel vs minute assignments and alert lights for any changes (3) BNC output of 1 Hz master sync pulse (4) Power supply fuse, power-on LED (5) LED display for microprocessor alarm (6) LED display for Daylight Saving Time on, leap second pending (7) Button to display next scheduled DUT1 correction value. Page 12 of 15 3.0 DESIGN REQUIREMENTS 3.1 Safety The equipment shall include those electrical, mechanical and operational design characteristics and features required to assure protection of personnel and equipment from inherent and accidentally induced hazards. 3.2 Reliability The operational reliability of the equipment is of major importance. The contractor shall maintain a continuous surveillance of the manufacture of parts and assemblies by qualified quality-control personnel. The use of solid-state devices of proven reliability is preferred. Neon or incandescent lamps shall not be used. All code conversion logic shall use solid-state circuitry. The offeror shall supply, as a part of his proposal on the equipment covered by this specification, a summary covering the design approach, a description of the circuitry used to perform the various functions, and a description of the processes followed to insure reliability. 3.3 Interchangeability All parts and components which have the same maunfacturer's part number shall be electrically interchangeable with each other with respect to performance and mechanical fit. 3.4 Human Factors Criteria The equipment design shall reflect full consideration of human factors and shall use applicable guidelines and data of modern human-interface engineering. The offeror should provide, as part of his proposal package, as much detail as possible on the software and user-interface aspects affecting the operational use of the system. The "user friendliness" of the system will be an important factor in rating the proposals. 3.5 Power Source The equipment shall operate properly from a 117 (+/- 10%) VAC, 50 to 60 Hz, single-phase power source. The maximum power drawn from the source shall not exceed 110 watts. Each time code generator shall have the capability of supplying power to an external load at 5 volts DC, 800 milliamperes. Each time code generator shall be capable of continuing time accumulation for at least four hours when operating from an external battery of nominally 18 volts during a loss of primary power. Connections for the +5 volts output and the 18 volt (battery) input shall be via a type MS3102A14S-6P Cannon/Amphenol connector on the rear panel, or other such six-pin connector capable of mating with existing type MS3106B14S-6S Page 13 of 15 Cannon cable connectors. The wiring of the chassis-mounted connector shall be as follows: Pin A: No connection Pin B: +5 volts DC out Pin C: Ground Pin D: Ground Pin E: +18 volt (battery) in Pin F: +18 volt (battery) in Upon restoration of primary power, the system must automatically resume all operations as it was performing them prior to power loss. Voltage supplied to the time code generator from the power supply and batteries shall show no level shift or transients as a result of change from line to batteries or vice-versa. Circuitry shall be provided for an alarm indication in case of failure of all operating power. This shall be provided via a four- pin rear-panel connector as follows: Pins 1 and 2: Normally open and ground Pins 3 and 4: Normally closed and ground A power-alarm condition shall be indicated by a reversal of these pairs to their opposite states. It is permissible to use a mechanical relay for these closures. 3.6 Mechanical Requirements 3.6.1 Dimensions The equipment shall be furnished for mounting in a standard cabinet, rack, or console sized for panels 19 inches wide and equipment 24 inches deep. Maximum depth behind the front panel, including connectors, shall not exceed 21 inches. Height shall not exceed 7 inches. 3.6.2 Construction Solid-state circuitry mounted on plug-in, etched-circuit boards shall be used. Easy access shall be provided to all circuit cards and their connectors. Wire-wrap or soldered connections will be allowed for wiring between plug-in circuit card connector terminals in lieu of a mother-board PC board. Plug-in circuit cards shall be of glass-epoxy construction. An AC line filter shall be used to reduce the effects of power line noise upon equipment operation. The chassis side panels shall be readily adaptable to commercial slider assemblies, which shall be furnished by bidder. The equipment shall be constructed and finished in a thoroughly Page 14 of 15 workmanlike manner. Attention shall be given to neatness and thoroughness of soldering, wiring, marking of parts and assemblies, plating, painting, and freedom of parts from burrs and sharp edges. 3.6.3 Finish Materials shall be suitably processed to resist corrosion. The use of any protective coating that will crack, chip, or scale with age or exteremes of climate or environmental conditions as specified herein shall be avoided. All finished surfaces shall be smooth, continuous, and free of runs, bubbles, or other irregularities. 3.6.4 Accessories Furnished All A.C. power cables, interconnecting cables between time- code unit and power supply, power cable for comparator unit, and any other items necessary for normal operation shall be furnished by bidder. 3.7 Electromagnetic Interference The equipment operation shall not be adversely affected by electromagnetic fields produced by external equipment which has been suitably designed to minimize conducted and radiated electromagnetic energy. The equipment shall not be a source of electromagnetic interference to nearby equipment. 4.0 ENVIRONMENTAL REQUIREMENTS 4.1 General The equipment shall withstand, with no physical damage or performance degradation, any natural combination of environmental conditions defined in the following paragraphs. 4.2 Operating Environment 4.2.1 Temperature -20 C to +55 C. The units shall be designed to allow forced air cooling from an external system for operation at temperatures greater than +40 C. No internal fans or blowers shall be used. 4.2.2 Humidity Up to 95% relative humidity. Page 15 of 15 4.2.3 Altitude Sea level to 10,000 feet. 4.2.4 Salt atmosphere As found in coastal regions. 4.3 Shock and vibration The equipment shall withstand shock and vibration as encountered during transportation by commercial moving van and commercial aircraft. 5.0 MAINTAINABILITY REQUIREMENTS The equipment shall be so designed that field maintenance and service requirements are minimized. The equipment shall employ modular construction to permit the rapid location and replacement of malfunctioning units in the field. Plug-in circuit boards shall be easily inserted or removed without the use of special tools. Tools and test equipment, not normally found in a well equipped electronic laboratory, and which are required to install, calibrate, maintain, or repair the equipment shall be supplied with the equipment. Manuals Three copies of a complete operating and maintenance instruction manual shall be furnished. The manual shall include equipment specifications and sections describing the installation, operation, theory of operation, and maintenance, procedures. Logic diagrams for the equipment and schematics and specifications of all circuits used shall be included. A bill of materials listing all parts used by description, maufacturer, manufacturer's part number, and quantity used shall be included.