1) Dual signs signifies foreign travel.
2)12th house is a house of foreign residence. I guess the logic behind it is the 12th house is the 4th house(residence) from the 9th house(foreign travel). It is also 9th from 4th.
3) Ketu and Jupiter are also the significators of foreign travel. I guess the logic behind Jupiter being a significator of foreign travel is Jupiter is the lord of 9th (Sagittarius) and 12th (Pisces) signs of the Kalpurush zodiac.
4) Malefic influences on the 2nd house of family can result in either of the following:
• Foreign travel: If malefic influences on the 2nd house are supported by other strong connections for foreign travel in the birth chart then the native will leave his/her family and travel abroad.
• Short journey: If malefic influences on the 2nd house are supported by other strong connections for short journeys but not foreign travel then the native will leave his/her family and make short journeys.
• No travels but conflicts with family: If malefic influences on the 2nd house are not supported by other strong connections for foreign travel or short journeys in the birth chart then the native will have conflicts with his/her family but won’t leave them for foreign travel.
5) Malefic influences on the 4th house of home can result in either of the following:
• Foreign travel: If malefic influences on the 4th house are supported by other strong connections for foreign travel in the birth chart then the native will leave his/her family and travel abroad.
• Short journey: If malefic influences on the 4th house are supported by other strong connections for short journeys but not foreign travel then the native will leave his/her home and make short journeys.
• No travels but conflicts with family: If malefic influences on the 4th house are not supported by other strong connections for foreign travel or short journeys in the birth chart then the native will have an unhappy domestic life but won’t leave his/her for foreign travel or short journeys.
6) The dasha of the 7th lord or planets in the 7th house can give foreign travel.
7) If the lagna makes connection with 7th house, 9th house or 12th house but these connections happen in fixed signs then the person will make short journeys within the country and not to a foreign land.