✅Answer: There are two guidelines narrated for a traveler regarding the 'adhan' and 'iqama' for his prayers, which are presented:

1 عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِی عَبْدِ اللَّهِ عَنْ أَبِی عَبْدِ اللَّهِ قَالَ سَمِعْتُهُ یَقُولُ یُقْصَرُ الْأَذَانُ فِی السَّفَرِ کَمَا تُقْصَرُ الصَّلَاةُ تُجْزِی إِقَامَةٌ وَاحِدَةٌ

📚Tahdhib, Vol. 2, p. 51

Translation: Abd al-Rahman said: I heard Imam Sadiq (peace be upon him) say: 'While traveling, just as the prayer is shortened, the 'adhan' is also shortened (in this way), a single 'iqama' is sufficient (without the 'adhan').'

2 الْحُسَيْنُ بْنُ سَعِيدٍ عَنِ الْقَاسِمِ بْنِ عُرْوَةَ عَنْ بُرَيْدِ بْنِ مُعَاوِيَةَ عَنْ أَبِي جَعْفَرٍ قَالَ الْأَذَانُ يُقْصَرُ فِي السَّفَرِ كَمَا تُقْصَرُ الصَّلَاةُ الْأَذَانُ وَاحِداً وَاحِداً وَ الْإِقَامَةُ وَاحِدَةً وَاحِدَةً

📚Tahdhib, Vol. 2, p. 62

Translation: Imam Baqir (peace be upon him) said: 'While traveling, the 'adhan' is shortened just as the prayer is shortened (in this way), the phrases of the 'adhan' are one by one, and the phrases of the 'iqama' are also one time each.'

✅Of course, due to the following hadith, acting upon the first hadith is better, more well-known, and more in line with the generalities of the narrations:

3 عَنِ الْحُسَیْنِ بْنِ سَعِیدٍ عَنْ فَضَالَةَ عَنْ حُسَیْنِ بْنِ عُثْمَانَ عَنِ ابْنِ مُسْکَانَ عَنْ بُرَیْدٍ مَوْلَی الْحَکَمِ عَمَّنْ حَدَّثَهُ عَنْ أَبِی عَبْدِ اللَّهِ عقَالَ سَمِعْتُهُ یَقُولُ لَأَنْ أُقِیمَ مَثْنَی مَثْنَی أَحَبُّ إِلَیَّ مِنْ أَنْ أُؤَذِّنَ وَ أُقِیمَ وَاحِداً وَاحِداً

📚Tahdhib, Vol. 2, p. 62

Translation: The narrator said: I heard Imam Sadiq (peace be upon him) say: 'If I only say the 'iqama' and say its phrases two times each, it is more beloved to me than if I say both the 'adhan' and the 'iqama' and say their phrases one by one.'

✅Note: Also pay attention to the following narration:

4 عَنْ مُحَمَّدِ بْنِ الْحَسَنِ عَنِ الصَّفَّارِ عَنْ مُحَمَّدِ بْنِ عَبْدِ الْحَمِیدِ وَ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ عِیسَی جَمِیعاً عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ أَبِی نَصْرٍ الْبَزَنْطِیِّ عَنْ صَفْوَانَ بْنِ مِهْرَانَ عَنْ أَبِی عَبْدِ اللَّهِ قَالَ الْأَذَانُ مَثْنَی مَثْنَی وَ الْإِقَامَةُ مَثْنَی مَثْنَی وَ لَا بُدَّ فِی الْفَجْرِ وَ الْمَغْرِبِ مِنْ أَذَانٍ وَ إِقَامَةٍ فِی الْحَضَرِ وَ السَّفَرِ لِأَنَّهُ لَا یُقَصَّرُ فِیهِمَا فِی حَضَرٍ وَ لَا سَفَرٍ....

📚'Ilal al-Shara'i', Vol. 2, p. 337

Translation: Imam Sadiq (peace be upon him) said: 'The phrases of the 'adhan' are two times each and the 'iqama' is also two times each, and for the Fajr and Maghrib prayers, whether at home or on a journey, there is no escape from the 'adhan' and 'iqama' because the Fajr and Maghrib prayers are not shortened or reduced at home or on a journey...'

✅According to the above narration, the 'adhan' and 'iqama' for the Fajr and Maghrib prayers do not change whether at home or on a journey and are said in full in both cases.

اللَّهُمَّ فَصَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْرَ