Question: what is the function of the ptt button on a two-way radio
[{'answer': 'push - to - talk', 'provenance': [{'wikipedia_id': '804074', 'title': 'Two-way radio', 'start_paragraph_id': 67, 'start_character': 75, 'end_paragraph_id': 67, 'end_character': 94, 'bleu_score': 1.0, 'section': 'Section::::Types.:Push-to-talk (PTT).\n'}]}, {'provenance': [{'wikipedia_id': '804074', 'title': 'Two-way radio', 'start_paragraph_id': 66, 'start_character': 0, 'end_paragraph_id': 66, 'end_character': 820, 'bleu_score': 0.9866213202385071, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16688950424477974861}, 'section': 'Section::::Types.:Push-to-talk (PTT).\n'}]}]