Abstract: An apparatus for welding closed one end of each of a multiplicity of open-ended tubes suitable for use as brachytherapy capsules includes a welding station having a welding position for welding closed one end of a tube, a rotatable platform having an outside edge, a tube holder positioned adjacent the outside edge, the tube holder movable between a loading position and the welding position, and a feed line positioned in overlying registry with the tube holder at the loading position.

Abstract: In a method for welding closed one end of each of a multiplicity of open-ended tubes suitable for use as brachytherapy capsules (100), each tube is loaded into a holder (52), brought to a welding station (80), has one end welded closed and is then released from the holder (52). A number of holders can be arranged on the periphery of a rotatable member (50), each holder being loaded with a tube at a first station, and then carrying the tube to a welding station (80) and an ejection station (90). The tubes can be loaded into the holders individually by means of an escapement mechanism (40).

Abstract: In a method for welding closed one end of each of a multiplicity of open-ended tubes suitable for use as brachytherapy capsules (100), each tube is loaded into a holder (52), brought to a welding station (80), has one end welded closed and is then released from the holder (52). A number of holders can 2 be arranged on the periphery of a rotatable member (50), each holder being loaded with a tube at a first station, and then carrying the tube to a welding station (80) and an ejection station (90). The tubes can be loaded into the holders individually by means of an escapement mechanism (40). The invention also extends to apparatus for carrying out the method.

Abstract: A digital-to-analog converter capable of bi-directional output currents which is especially useful for direct conversion of digitally encoded audio signals. The converter is made up of a plurality of bit-cell circuits, one per bit in the digital number to be decoded, each fed by a pair of current sources of identical magnitude and opposite direction. Each bit-cell is a bridge circuit of four controllable devices, controlled by a data bit and its complement so that the current flow through the current output of the cell reverses based upon the value of the data bit. The outputs of the bit-cells are paralleled, and the current source pairs are scaled in a binary fashion, so that each bit-cell steers a current which is one-half that of the next-higher cell.In a preferred embodiment, the current sources are made up of two binary scaled current generators using R-2R resistor networks to scale currents from two reference sources. The two references are preferably linked to each other through a feedback circuit.