with any of these models are also supported. MTS also supports access from 10- or 12-button touch-tone telephones via the IBM 7772 Audio Response Unit and later the Votrax Audio Response Unit,<ref>"The University of Michigan Audio Response System and Speech Synthesis Facility", Edward J. Fronczak, Second USA Japan Computer Conference, Proceedings, pp. 380-84, 1975</ref> IBM 1052 consoles, IBM 3066 console displays, and IBM 3270 family of locally attached displays (IBM 3272 and 3274 control units, but not remote 3270 displays). Front-end communication processors MTS can and does use communication controllers such as the IBM 2703 and the Memorex 1270 to support dial-in terminals and remote batch stations over dial-in and dedicated data circuits, but these controllers proved to be fairly inflexible and unsatisfactory for connecting large numbers of diverse terminals and later personal computers running terminal emulation software at ever higher data rates. Most MTS sites choose to build their own front-end processors or to use a front-end processor developed by one of the other MTS sites to provide terminal support. These front-end processors, usually DEC PDP-8, PDP-11, or LSI-11 based with locally developed custom hardware and software, would act as IBM control units attached to the IBM input/output channels on one side and to modems and phone lines on the other. At the University of Michigan the front-end processor was known as the Data Concentrator (DC). The DC was developed as part of the CONCOMP project by Dave Mills and others and was the first non-IBM device developed for attachment to an IBM I/O Channel. Initially a PDP-8 based system, the DC was upgraded to use PDP-11 hardware and a Remote Data Concentrator (RDC) was developed that used LSI-11 hardware that connected back to a DC over a synchronous data circuit. The University of British Columbia (UBC) developed two PDP-11 based systems: the Host Interface Machine (HIM) and the Network Interface Machine (NIM). The University of Alberta used a PDP-11 based Front-end processor. These front-end systems support their own command language of "device commands", usually lines prefixed with a special character such as a percent-sign (%), to allow the user to configure and control the connections. The $CONTROL command and programs running on MTS can use the CONTROL subroutine to issue device commands to front-end and network control units. Network support Over time some front-ends evolved to provide true network support rather than just providing support for connections to