1. Do they have many legs?
2. What are they used in...like Amplifier, Computer etc. Please state device.
3.What color are they?
4.Three legs and black would suggest maybe some sort of Transistor or maybe a little Mosfet.
Sorry, I forgot to ask how big they are. Please indicate some sort of size info.
Give answers to my questions above and I will know Exactly what they are
Can you tell which of the legs on the 10S25 are power in, power out, and ground? What are its other connections? Are you sure it is not an oscillator or opamp? Are you sure of the number? Could the "1" be a "7."
remember to transliterate letters because Soviets use Kirilic.
this means that your "H" is not H but "N" (Which is Kirilic looks like Latin "H").
this is why above site will return 'no match" if you search for 1HT251 (Latin) but it will find two matches if you search for 1НТ251 (Kirilic).
same goes for T which appears to be the same as Т but while they both represent same letter, it is a different character and enough to not find any matches.
one easy way is to just copy and paste those character from Kirilic text of the page itself.
one you know this, Google will be able to find it too (try to copy and paste 1НТ251 ).
btw "looks like regulator" means nothing to me. regulators can be different devices and they come in variety of packages and configurations. don't you have camera on your computer or phone?