Ok, you have beaten me with evidence. I used google translate on http://www.ekeving.se/hi/sj-regl-1858.html
a few points that I had missed before:
1858 - T signal is clearly a time interval signal, with caution displayed 5 minutes after a train has passed. Nothing about points, so it may have been used as start signal in time interval method. Disc signal was described only in text.
1877 - T signal shows only danger and caution, stop 100m before the signal or points. Signal all well (clear) was replaced with hand given flag signals. This may be the split when T-signal became solely home signal, and start signal was given by hand.
1888 - First stellverk (signalbox) - operating points and disc signals
1890 - two arm semaphore exists, but rules updated in 1905, 3-wing 1907
And here it goes: Semaphores occurred mainly as entrance signals. When they were not designed as T-semaphores they were placed about 50 meters outside the outer gear.
Utfartssemafor (departure / start signal) was used mainly on branch stations, where multiple arms indicated which branch is clear (similar to early czechoslovak start signals).
Start signals were used also in the few lines with block systems, moving bridges and remote sidings. Last t-signal was abolished at siding in Skahus in 1980
1905 - T-signals still in rules, but also one-sided signals and two-armed one-sided signals, lower quadrant
Already in 1906 it was decided that the movement authority would appear with wings upward instead, this was carried out in 1915 by SJ.
Since the Royal. Railway Board, as December 1, 1906 established new signal sequence (upper quadrant) to effect from October 1, 1907
Disc signals disappeared from SJ in 1923. From 1915 onwards introduced försignaler more generally, and the entrance gate signals shifted to about 200 meters outside the outer gear.
It seems that we have several distinct working methods for T-signals.
- ffestiniog type - start signal for both directions - in the middle of station. Arriving train can pass this signal on danger, but must stop at the platform (within station / few meters before points).
methods - token block or staff+ticket (time interval with telegraph).
Accompanying home (and distant) signal is of disc/plate type, that can be remotely operated by wires.
This probably fits also earliest swedish practice (1858)
- swedish type (1877) - home signal for both directions - in the middle of station. Train must stop outside the stations furthest points. methods - time interval (w/wo telegraph), absolute + token block, choose signal. I have really big doubts with this concept, due to possible visibility problems, especially in the absence of distant signals. Perhaps the plate signal was used as home signal, if the T-signal could not be seen from big distance.
Departure signalled by hand.
- swedish usage outside of station - signal guarding a siding - look at last 3 photos at http://www.ekeving.se/si/mek/T-sem/T-sem.html the signal is at a switch - either a first switch of station, but more probably it is just a simple (rarely used) siding in the middle of nowhere. Note that it shows clear in both directions (!). It will be probably set to danger only if there are some movements to/from the siding.
Similar is the 4-directional beast. It says "crossing of normal and narrowgauge in Norrköping" .
Also very interesting is the other 4-armed thing - IMHO it works as a 3-armed home signal in one direction and 1 armed start signal in the other. These examples make much more sense to me than the T-signal in the centre of station.
- austro-hungarian type - block signal (either absolute block or time interval) - just to save on construction and maintenance costs. No special rules, train has to stop in front of that signal. Never seen such signal in the middle of station.
Even today on czech and slovak railwayes, there are color light signals facing both directions on both sides of double track lines, so that both tracks can be used in both directions.
One old picture suggests that it could have been used at sidings or points as well, but there is no explaining text.