AT&T Microelectronics Inc has acquired worldwide marketing rights for the desktop ISDN chip it developed under contract from Sun Microsystems Computer Corp and has contracted with CoSystems Inc of Santa Clara, California to provide marketing and technical support for the device: the company says the arrangements are designed to speed delivery to market of ISDN-ready desktop computers using the single-chip T7259 device, which was developed for the SparcStation 10; AT&T also developed a dual transformer, the 2768A, specifically for the T7259 which terminates the loop properly and protects the chip through electrical isolation; the part supports control of up to eight desktop ISDN devices, such as telephones, videophones, and facsimile machines, includes a high speed serial interface providing direct connection to audio and multimedia chips for traffic over the ISDN Basic Rate Interface; on-chip 16-channel Sbus DMA control, providing high speed connection between multimedia chips and memory; on-chip multichannel HDLC controller, supporting D channels from the TE and NT interfaces and up to 14 additional independent HDLC channels; programmable FS signal and clock, supporting various types of external coder-decoder; and standard four-wire ISDN interface to the network, enabling one design to be marketed internationally; the T7259 device is $95 in 1,000-up quantities through AT&T; smaller quantity orders and samples are available from CoSystems.