Swedish railroad signals and signsNot complete, just an overview.
Main signals1 red = stop
1 green = go (80 km/h which is maximum speed unless you've got ATC)
2 green = go 40 km/h
3 green = go 40 km/h but you'll have to stop shortly after
Distant signals1 flashing green = next signal shows stop
2 flashing green = next signal shows go 40
1 flashing white = next signal shows go
no light at all = consider it as next shows stop
This has historical background because in the beginning green meant "stop" and white meant "go".
Both main and distant signals may be combined or stand alone. This means a main signal can have 2 - 5 lights and a distant only 2 or 3 lights.
Instead of distant signal there can be a sign warning that there will be a main signal in 800-1000 m (or with an additional sign stating the distance). It looks like a black triangle with yellow border over a round sign looking like a distant signal without lights (black circle with white segments left and right).
At the road crossing there's a signal with a "V" below (väg = road)
1 red = stop if possible
1 white = gates are down and/or red flashing light shown for road traffic. Optionally also no vehicle detected on the track. (Not green because road traffic isn't under positive control like other rail traffic.)
Distant road crossing3 flashing yellow in triangle = next road crossing shows red
3 yellow in triangle = next road crossing shows white
Road crossing alertBlack triangle with yellow border over a yellow sign with a "V" = when you pass this the distant road crossing signal should show OK to pass. (Meaning between here and the road crossing you can brake to a stop but not if you start braking at the distant signal.)
Bridges (like road crossing but with bridge icon instead of "V")
1 red = stop
1 white = bridge is not open
ATCWhite or yellow square tilted 45 deg with a black circle marks a place where ATC can send changes.
Speed limitsYellow circle with black numerals.
ATC speed limit signs are shown as a black arrow, either alone or together with one showing km/h for non-ATC. Pointing down if speed limit is lower otherwise up.
Black triangle with yellow border over a rectangular yellow sign with numerals means there's speed limit sign with that speed in about 1000 m.
HornBlack triangle with white border, pointing down = sound the horn for 3 seconds.
Can have additional sign saying only give signal between 06:00 and 22:00.
Can have additional sign "V" meaning horn should give sound again about halfway to the crossing. In bad visibility many times between the sign and the crossing.
At a platform
Flashing "A" = depart
Flashing red = stay
Square with horizontal black and white lines = lift snow plow.
SourcesTwo sources with illustration: Wikipedia in English and Banguide in Swedish. And a really good one showing signals' placement along the track.
Also the official document.