# Standard frequency and time signal service

Standard frequency and time signal service (short: SFTS) is, according to Article 1.53 of the International Telecommunication Union's (ITU) Radio Regulations (RR), "A radiocommunication service for scientific, technical and other purposes, providing the transmission of specified frequencies, time signals, or both, of stated high precision, intended for general reception".

## Classification

In accordance with ITU Radio Regulations (article 1) variations of this radiocommunication service are classified as follows: Standard frequency and time signal service (article 1.53)
* Standard frequency and time signal-satellite service
In general this radiocommunication service uses radio stations as follows:
* Standard frequency and time signal stations (article 1.95)

## Standard frequency and time signal-satellite service

Standard frequency and time signal-satellite service (short: SFTSS) is, according to Article 1.54 of the International Telecommunication Union's (ITU) Radio Regulations (RR), defined as A radiocommunication service using space stations on earth satellites for the same purposes as those of the standard frequency and time signal service.
An example to this were experiments of time synchronisation (Global Transmission Services GTS-2) onboard International Space Station. However, in accordance to the ubiquitous availability, GNSS-satellite signals will be used in practice (see also: GPS disciplined oscillator).

## Frequency allocation

The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012).
In order to improve harmonisation in spectrum utilisation, the majority of service-allocations stipulated in this document were incorporated in national Tables of Frequency Allocations and Utilisations which is with-in the responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared.
* primary allocation: is indicated by writing in capital letters (see example below)
* secondary allocation: is indicated by small letters

### Example of frequency allocation

Allocation to services :
* Region 1
* 19.95–20.05 MHz        STANDARD FREQUENCY AND TIME SIGNAL (20 MHz) ||
* 2 498-2 501 MHz        STANDARD FREQUENCY AND TIME SIGNAL (2 500 MHz) ||
* 4 995–5 003 MHz        STANDARD FREQUENCY AND TIME SIGNAL (5 000 MHz) ||
* 5 003–5 005 MHz        STANDARD FREQUENCY AND TIME SIGNAL
* Space research ||
* 9 995–10 003 MHz      STANDARD FREQUENCY AND TIME SIGNAL (10 000 MHz) ||
* 10 003–10 005 MHz    STANDARD FREQUENCY AND TIME SIGNAL
* Space research ||
* 14 990–15 005 MHz    STANDARD FREQUENCY AND TIME SIGNAL (15 000 MHz) ||
* 15 005–15 010 MHz    STANDARD FREQUENCY AND TIME SIGNAL
* Space research ||
* 19 990–19 995 MHz    STANDARD FREQUENCY AND TIME SIGNAL
* Space research ||
* 19 995–20 010 MHz    STANDARD FREQUENCY AND TIME SIGNAL (20 000 MHz) ||
* 24 990–25 005 MHz    STANDARD FREQUENCY AND TIME SIGNAL (25 000 MHz) ||
* 25 005–25 010 MHz    STANDARD FREQUENCY AND TIME SIGNAL
* Space research ||

## Time signals in use

The following are the known HF time signal stations currently operational.
| Call Sign | Location | Frequencies | Notes |
| ITU-R Standard Frequency and Time Signal services ||||||
| BPM | Pucheng, China | 2.5, 5, 10, & 15 MHz | ITU-R TF.768-5 |
| BSF | Chung-Li, Taiwan, Rep. of China | 5 and 15 MHz | |
| EBC | Cádiz | 4.998 MHz | |
| HLA | Taejon, Republic of Korea | 5 MHz | ITU-R TF.768-5 |
| IAM | Rome, Italy | 5 MHz | ITU-R TF.768-5 |
| LOL | Buenos Aires, Argentina | 5, 10, & 15 MHz | ITU-R TF.768-5 |
| MIKES | Espoo, Finland | 25 MHz | |
| OMA | Prague, Czech Republic | 2.5 MHz | Discontinued in 1995 |
| PPE | Rio de Janeiro, Brazil | 10 MHz | |
| RWM | Moscow, Russia | 4.996, 9.996, 14.996 MHz | ITU-R TF.768-5 |
| WWV | Fort Collins, Colorado, United States | 2.5, 5, 10, 15, & 20 MHz | ITU-R TF.768-5 |
| WWVH | Kekaha, Kauai, Hawaii, United States | 2.5, 5, 10, & 15 MHz | ITU-R TF.768-5 |
| YVTO | Caracas, Venezuela | 5 MHz | |
| Time signal stations on non-standard frequencies ||||||
| CHU | Ottawa, Ontario, Canada | 3.33, 7.85, 14.67 MHz | |

### United States

The Standard Time and Frequency Signal (STFS) is a Radiocommunication service providing the transmission of specified frequency and time signal, of stated high precision, intended for general reception in the United States and beyond. The radio signals are broadcast on very precise carrier frequencies by the U.S. Naval Observatory and the National Institute of Standards and Technology (NIST), formerly the National Bureau of Standards (NBS). The technical specification of that particular service is in line to the provisions of the International Telecommunication Union's (ITU) Radio Regulations (RR)