The adhan (call to prayer) of Bilal should not prevent you from taking a meal shortly before dawn, not does the whiteness of horizon (before dawn) in this way (vertically) until it spreads out horizontally.  

قَالَ رَسُولُ اللَّهِ ﷺ لاَ يَمْنَعَنَّ مِنْ سَحُورِكُمْ أَذَانُ بِلاَلٍ وَلاَ بَيَاضُ الأُفُقِ الَّذِي هَكَذَا حَتَّى يَسْتَطِيرَ  

[Machine] The Messenger of Allah ﷺ said, "Do not be deceived by your sahoor (pre-dawn meal) by the Adhan of Bilal or the whiteness of the morning. Like this." Then he raised his hands until they reached the sky and extended his hand."  

قَالَ رَسُولُ اللهِ ﷺ «لَا يَغُرَّنَّكُمْ مِنْ سُحُورِكُمْ أَذَانُ بِلَالٍ وَلَا بَيَاضُ الصُّبْحِ هَكَذَا وَرَفَعَ يَدَيْهِ حَتَّى يَطِيرَ فِي الْأُفُقِ وَعَرَّضَ بِيَدِهِ»  

The Adhan of Bilal may not mislead you with regard to your food at the commencement of the fast, nor the vertical (streaks) of whiteness in the horizon (for it is an indication of false dawn). You should stop eating (food) till (the whiteness) spreads like it. Hammad narrated it and with the gesture of his band he explained, the horizontal position (of the streaks of light). (Using translation from Muslim 1094c)   

قَالَ رَسُولُ اللهِ ﷺ لَا يَغُرَّنَّكُمْ مِنْ سُحُورِكُمْ أَذَانُ بِلَالٍ وَلَا بَيَاضُ الْأُفُقِ الْمُسْتَطِيلِ هَكَذَا حَتَّى يَسْتَطِيرَ هَكَذَا وَحَكَى حَمَّادٌ بِيَدِهِ قَالَ يَعْنِي مُعْتَرِضًا  

The Adhan of Bilal may not mislead you with regard to your food at the commencement of the fast, nor the vertical (streaks) of whiteness in the horizon (for it is an indication of false dawn). You should stop eating (food) till (the whiteness) spreads like it. Hammad narrated it and with the gesture of his band he explained, the horizontal position (of the streaks of light). (Using translation from Muslim 1094c)   

قَالَ رَسُولُ اللهِ ﷺ لَا يَغُرَّنَّكُمْ مِنْ سُحُورِكُمْ أَذَانُ بِلَالٍ وَلَا بَيَاضُ الْأُفُقِ الْمُسْتَطِيلُ حَتَّى يَسْتَطِيرَ هَكَذَا وَحَكَاهُ حَمَّادٌ بِيَدِهِ يَعْنِي مُعْتَرِضًا  

"لَا يَمْنَعَنَّ مِنْ سُحُورِكُمْ أذَانُ بِلالٍ، وَلَا بَيَاضُ الأُفُقِ هكذا حتى يَسْتَطيرَ".  

"لا يَغُرَّنكم فِي سحورِكم أذانُ بلالٍ، وَلا هذا البياضُ" وفي لفظ: "ولا بياضُ الأفق المستطيل حتى يستطيرَ".