What was a Terminal Concentration Device in DEC's products?

http://www.bitsavers.org/pdf/dec/qbus/EK-DHQ11-UG-002.pdf DHQ11 User Guide, EK-DHQ11-UG.002 The main application of the M3107 DHQ11 is for interactive terminal handling; it can also be used for data concentration and real-time processing. It has two programming modes, DHV11 and DHU11. The register sets in these modes are compatible with those of the DHV11 and DHU11 respectively. The preferred mode of operation is DHU11 mode. The main features of the DHQ11 are: ? For transmission: DMA transfers; or for each line, program transfers to a 1 character transmit buffer in DHV11 mode, or to a 64-character transmit FIFO in DHU11 mode ? For receive: a 256-entry FIFO buffer for received characters, dataset status changes, and diagnostic information The M3118 CXA16 and the M3119 CXA08 have the same programming interface as the M3107 DHQ11 The M3108 DSV11 can do DMA transfers in both directions, although it is a synchronous interface, not asynchronous. http://www.bitsavers.org/pdf/dec/qbus/EK-DSV11-TM-001_Jan87.pdf DSV11 Technical Manual, EK-DSV11-TM-001 Functional Description (Section 1.5). The DSV11 supports a range of synchronous protocols on the serial interface, and transfers data to and from the host by DMA transfer. This section describes the way in which the DSV11 handles data. On Sat, Jan 29, 2022 at 3:49 PM Chris Zach via cctalk <cctalk at classiccmp.org> wrote: