να σου εξηγησω μια και ειμαι σιδηροδρομικος..
οταν στον πειραια γινοταν συγχρονισμος ρολογιων αυτος γινοταν ταυτογχρονα σε ολους τους σταθμους μεχρι τον εβρο..τα ρολογια αυτα ηταν συγκεκριμενων προδιαγραφων που ζητουσε ο οργανισμος..
σημερα η πιστοποιηση ενος υλικου γινεται απο οργανισμους οι οποιοι ελεγχουν αν το υλικο είναι συμβατο με τις προδιαγραφες ..πχ το ISO..
τα σιδηροδρομικα ρολογια ειναι 24ωρα συνηθως ..για παραδειγμα
A typical railroad's requirements for a watch in the early 20th century might include:
only American-made watches may be used (depending on availability of spare parts)
only open-faced dials, with the stem at 12 o'clock
minimum of 17 functional jewels in the movement
16 or 18-size only
maximum variation of 30 seconds (approximately 4 seconds daily) per weekly check
watch adjusted to at least five positions: Face up and face down (the positions a watch might commonly take when laid on a flat surface); then crown up, crown pointing left, and crown pointing right (the positions a watch might commonly take in a pocket). Occasionally a sixth position, crown pointing down, would be included.
adjusted for severe temperature variance and isochronism (variance in spring tension)
indication of time with bold legible Arabic numerals, outer minute division, second dial, heavy hands,
lever used to set the time (no risk of inadvertently setting the watch to an erroneous time, when winding the watch with the stem)
Breguet balance spring
micrometer adjustment regulator
double roller escapement
steel escape wheel
anti-magnetic protection (after the advent of diesel-electric locomotives)
The minimum requirements were raised several times as watch-making technology progressed, and the watch companies produced newer, even more reliable models. By World War II, many railroads required watches that were of a much higher grade (as many as 23 jewels, for example) than those made to comply with the original 1891 standard.[3]
