PTB Modem Time Service and other European Laboratories Time Services
Last update: May 3, 2023 17:13 UTC (e8077bcf6)
Table of Contents
Synopsis
- Address:
127.127.23.u
- Reference ID:
PTB
- Driver ID:
ACTS_PTB
- Serial Port:
/dev/ptbu; 1200 baud, 8-bits, no parity
- Requires:
/usr/include/sys/termios.h header file with modem control
Description
This driver supports the PTB Automated Computer Time Service (ACTS) and is a modified version of the NIST ACTS driver.
It periodically dials a prespecified telephone number, receives the PTB timecode data and calculates the local clock correction. It is designed primarily for use when neither a radio clock nor connectivity to Internet time servers is available. For the best accuracy, the individual telephone line/modem delay needs to be calibrated using outside sources.
The only change between this driver and the NIST one is the data format. In fact PTB data format is the following:
Data format
0000000000111111111122222222223333333333444444444455555555556666666666777777777 7
0123456789012345678901234567890123456789012345678901234567890123456789012345678 9
1995-01-23 20:58:51 MEZ 10402303260219950123195849740+40000500 *
A B C D EF G H IJ K L M N O P Q R S T U V W XY Z‹CR›‹LF›
A year
B month
C day
D hour
E : normally
A for DST to ST switch first hour
B for DST to ST switch second hour if not marked in H
F minute
G second
H timezone
I day of week
J week of year
K day of year
L month for next ST/DST changes
M day
N hour
O UTC year
P UTC month
Q UTC day
R UTC hour
S UTC minute
T modified julian day (MJD)
U DUT1
V direction and month if leap second
W signal delay (assumed/measured)
X sequence number for additional text line in Y
Y additional text
Z on time marker (* - assumed delay / # measured delay)
‹CR›!‹LF› ! is second change !
This format is an ITU-R Recommendation (ITU-R TF583.4) and is now available from the primary timing centres of the following countries: Austria, Belgium, Germany, Italy, The Netherlands, Poland, Portugal, Romania, Spain, Sweden, Switzerland, Turkey, United Kingdom. Some examples are:
Fudge Factors
time1 time-
Specifies the time offset calibration factor, in seconds and fraction, with default 0.0.
time2 time-
Not used by this driver.
stratum number-
Specifies the driver stratum, in decimal from 0 to 15, with default 0.
refid string-
Specifies the driver reference identifier, an ASCII string from one to four characters, with default PTB.
flag1 0 | 1-
Not used by this driver.
flag2 0 | 1-
Not used by this driver.
flag3 0 | 1-
Not used by this driver.
flag4 0 | 1-
Not used by this driver.
A keyword in the ntp.conf file permits a direct connection to a serial port of source of time like IEN CTD signal. It is sufficient to use the string DIRECT in place of the phone number.
Example:
server 127.127.23.1
phone DIRECT
Reference Clock Drivers