{{ALS162 Transmitter located in Allouis (Cher)}}

The time signal generated by the Allouis transmitter ALS162 (162 kHz), formerly France-Inter long waves, is one of the means of making legal time available in metropolitan France. This signal is used by many users (transport, energy, telecommunications, local authorities, individuals, etc ...) to synchronize more than 200,000 clocks.

Following the end of the broadcast of radio programs by Radio France in late December 2016, the ANFR (Agence Nationale des Fréquences) was commissioned by the government to ensure the broadcast of the signal. The signal transmitter ALS162, operated by TDF (Télédiffusion de France), is located in Allouis (Cher).

The signal carrier as well as the time code are referenced to cesium thermal beam clocks, provided by LNE-SYRTE, connected by common GPS views to the UTC(OP) time scale which is generated by LNE-SYRTE at Observatoire de Paris and which is at the basis of the legal time in France. The operational maintenance of the time and frequency equipment at the Allouis transmitter is ensured by France Horlogerie - Industrie du temps et des microtechniques, which acts on behalf of the group of manufacturers of radio synchronization equipment for the broadcast of the time legal in metropolitan France.

The monitoring of ALS162 signal is jointly conducted by LNE-SYRTE, LNE-LTFB and France Horlogerie. LNE-SYRTE monitors the carrier phase (frequency accuracy of 10^-12), which is used for some industrial calibrations, as well as the time signal (1 ms accuracy) as received at Observatoire de Paris. The reference for this monitoring is the UTC (OP) time scale produced by the LNE-SYRTE at the Observatoire de Paris. The LNE-LTFB ensures the connections between the thermal beam atomic clocks of the transmitter and UTC (OP) using the SYREF system, and monitors the validity of the TOD (Time of day) information as received at the Observatoire de Besançon. LNE-SYRTE publishes its measurement results in real time. These results are also included in Bulletin H, published monthly.

For more information on the coded time of the ALS162 signal:
Bulletin BNM n°63-64 p120 1986
L’onde électrique vol60 n10 1980
(NB: some systems have evolved since these publications).

See also the document on the accuracy of ALS162 signal