Editing Phoenix (computer) (section)

== Communications ==
The IBM-supplied [[Telecommunications Access Method]] (TCAM) and [[communications controller]] were replaced in 1975 by a system, called Parrot, that was created locally by the staff of the Computer Laboratory, comprising their own software and a [[PDP-11]] complex.  Their goal in doing so was to provide a better user interface than was available with a standard IBM system, alongside greater flexibility, reliability, and efficiency.  They wanted to support 300 terminals.  The initial system, supplied in 1972, comprised the PDP-11 emulating an [[270x|IBM 2703 transmission control unit]], which TCAM communicated with just as though it were a 2703.  The PDP-11 was used instead of a bank of 2703s because for a projected 300 terminals a bank of 2703s was not scalable, too expensive, and inadequate for the Computing Service's needs, since it required [[paper tape]] readers and [[card punch]]es as well.  Even this solution proved to be unsatisfactory, and in 1975 TCAM was replaced by Parrot, with 200 terminals connected to the PDP-11, of which 80 could be simultaneously active.  For full technical details of Parrot, see the technical report by [[Philip Hazel|Hazel]] and Stoneley.<ref>{{cite journal|title=Parrot&nbsp;— A replacement for TCAM|author=[[Philip Hazel|P. Hazel]] and A.J.M. Stoneley|date=April 1976|url=http://www.cl.cam.ac.uk./techreports/UCAM-CL-TR-5.pdf|journal=Technical Reports|publisher=[[University of Cambridge Computer Laboratory]]|id=UCAM-CL-TR-5|access-date=22 January 2010}}</ref>