noun
main switchboard number; main telephone number
Used for the primary contact number of an organization, distinct from individual extension numbers.
会社の大代表に電話してください。
Please call the company's main number.
Compound of 大 (dai, 'big, main') and 代表 (daihyō, 'representative'). The reading だいだいひょう is a straightforward combination of the readings of the components.