To use a repeater you must program your radio with the repeater’s offset and tone. In other words the your radio must send the correct sub audible tone to the repeater on a specified frequency. This will open the repeater for your use but when the repeater re-transmits your signal it does so on another frequency. This is called the repeater’s offset. So to receive transmission from that same repeater your radio must be programmed with the offset receive frequency. (Sending on one frequency and receiving on another is called “Duplex” operation. Sending and receiving on the same frequency is called “Simplex” operation and is used for point to point communication with no repeaters involved. The term “ping’ is used in computer networks to check connectivity by sending data packets that are traced for and reply to the sender. I suppose the term could applied to radio communications when sending data by packet or digital radio. http://repeaterbook.com is an excellent reference for U.S. Repeater settings.