When two operators are trying to talk at once on the repeater, the resulting noise is known as a double. If you're in a conversation including several people, you can avoid this by passing to another ham by giving their name or call at the end of your transmission. This type of group conversation is called a round table. It is good practice not to use the repeater for conversations that can take place simplex. Simplex simply means talking directly with someone on a single frequency.
Repeaters use two frequencies.
There are many simplex frequencies from which to choose. This frees the repeater for those portable, mobile or too far away to communicate otherwise. A complete list of these frequencies can be found in the ARRL Repeater Directory. The BARS repeater is equipped with an autopatch. An autopatch is a device that allows hams to make telephone calls through the repeater.