2 The different kinds of signals

Carré (square)

Absolute stop signal that cannot be crossed. To be set alone or, before a switch point, in combination with a "slowdown reminder"

Carré violet (purple square)

Another absolute stop signal to be set on shunting yards

Sémaphore

Signal protecting access to a block. With the block manual system, it is therefore located in station exit and can control multiple lanes

Warning

Annoucement sign, warning of a next closed stop sign

Slowdown

Tells the engineer to reduce his speed to 30 km / h and warns of passage on a switch point

Slowdown reminder

Placed near or over a 'carré', it recalls the engineer's obligation to drive at 30 km / h

Mobile speed board (announcement)

Back-lit and erasable sign. Used in case of speed reduction superior to 40 kph.

Mobile speed board (announcement)

Back-lit and erasable sign. Used in case of speed reduction inferior to 40 kph.

Mobile speed board (execution)

Back-lit and erasable sign. Also displayed in the entry of station on unique track in case of crossing of trains.

Red disc

Signal of warning, informing of a close stop. The engineer immediately has to walk at sight. In conjunction with the "warning" signal, it is frequently met at the approach of stations on single-track lane.

Annoucement of a shunting zone

Back-lit and erasable sign. Indicates to the engineer that his train is going to be directed towards a shunting zone and that he has to adopt the speed of 20 kph.

There are many other fixed boards. For a complete vision, see the site : http://fr.wikipedia.org/wiki/Signalisation_ferroviaire_en_France (in french)