A riveting yoke assembly comprises a yoke, a force applying mechanism and a rivet forming device. The apparatus comprises time stamping means for time stamping received information packets in accordance with a time stamping clock reference, writing means for recording the information packets in accordance with a write clock reference and reading means for reproducing the information packets in accordance with a read clock reference. The apparatus may include slips having cavities to facilitate quick drill-out of the plug. The frequency multiplier circuits preferably use heterojunction barrier varactor diodes to eliminate the need for DC bias or idler circuitry. The melt contains nitrogen, at least one Group III element selected from the group consisting of gallium, aluminum, and indium, and at least one of alkali metal and alkaline-earth metal. The tone control logic is operable to continuously transmit a guard tone on the second communication interface responsive to receiving data on the first communication interface, comprising data representative of a guard tone.