Complex sentence: The People in Need Trust is a charity in the Republic of Ireland which has as its main fundraiser a Telethon, known as the RTÉ People in Need Telethon, which is broadcast by RTÉ, and supported by Eircom (formerly Telecom Eireann).
Split into simpler sentences: The People in Need Trust is a charity in the Republic of Ireland which has as its main fundraiser a Telethon, known as the RTÉ People in Need Telethon. The RTÉ People in Need Telethon is a telethon in Ireland which is broadcast by RTÉ, and supported by Eircom (formerly Telecom Eireann).