Downloading the time "NistTime" basics A number of places around the world offer a dial-up time service to anyone with a computer, modem and corresponding software. This program will dial the service offered by the US National Institute of Standards and Technology (NIST, formerly NBS) and set the Psion clock and or record the error. Other services that I have tried deliver a different format of data. I may consider extending the repertoire of service numbers to call in the future. However each call is very short and hence cheap. The UK service, in contrast, is on a premium-charge telephone number and runs at only 1200 baud. Dialling dialogue The initial dialogue shows the locale and the full number to be dialled, merely for confirmation. It also allows the 3-Link speed to be set up for modem transfers. The default of 19200 baud should be OK for Psion 3A. The only choices at this point are to Esc and leave the program, or to dial through the modem, or to go to a further dialogue to determine a prefix for dialling out via a PABX. Or, of course, view this help file. Place and Time Zone The location from which the call is being made and the country which is being called (USA) are shown so that the dialling prefixes, if any, can be verified. Similarly the time zone is shown because it will effect the calculation of local time. The time given by NIST is GMT or UTC. The zone is not merely the geographic one but includes Daylight saving if this is set by the "Clock" built-in application. Error handling The program endeavours to cope with problems with data from the modem. If the 3-Link is absent this is discovered immediately. If the modem does not respond then the program will time it out. The data from NIST contains "*" for accurate time signals. This must appear within the first 20 lines or the program will give up. The date and time is given in a simple fixed format and is simply decoded. If digits of the date or time are not in place then the erroneous input is displayed with the faulty characters indicated. If the date or time are faulty then just the input is shown. Adjustment The clock adjustment is made by the number of seconds shown in the dialogue. The time is NOT set to the localised NIST time, so any delay in answering the dialogue does not matter. There is no way of altering the adjustment that will be made. The log file The name of the log file is chosen using a special dialogue. If the file already exists then its contents may be replaced by the new single entry or the new entry added to the end. The file selection dialogue is repeated until the answers are consistent with the state of the file discovered. If the write fails, perhaps because the file is currently open, the dialogue is repeated ready for another attempt. If the dialogue is abandoned then clock adjustment, if it was requested, will already have taken place. Logging The logging of the current (UTC) time, error in seconds and whether the correction was applied does not currently have a defined purpose. It is intended in the future to support periodic adjustment to correct the average daily error. The current time is recorded in days and decimal days since 1/1/1970. Any calculation should be independent of changes in time zone. The indicator of whether a change was made is 1 for change and 0 for none, so it can be used as a multiplier of the error to get the alteration. Further reading The dial-up services are really intended for use via PCs so PC software is available from NIST. This software can be obtained for free ftp download from: time_a.timefreq.bldrdoc.gov or for $42 on diskette by post from: Office of Standard Reference Materials, NIST, Gaithersburg, MD, 20899, (301) 975-6776 Additional technical information The information given here about PC software and additional detail can be obtained direct from NIST by dialling the number that this program uses via a terminal emulator instead and sending a "?" character as directed. The international dialling prefix that this program uses is obtained using functions provided by the "World" built-in application. This assumes that the "home" location is correctly set up. It also temporarily alters the "Default country" that is set by the Control-Dialling menu entry from the System screen (to "USA"). If the program crashes this might not be reinstated and must be corrected by hand. However I have not discovered from the "Psionics" documentation how to extract the "dial-out" prefix as set up by that menu entry, hence the program offers its own dialog to establish the prefix for dialling via a PABX. About program and author "NISTtime" Version 1.0, written by Mike Coon of UK. Contact 106710.2362@compuserve.com Usual restrictions placed on freeware apply.