IBM 1009

The IBM 1009 Data Transmission Unit was an IBM communications controller introduced in 1960.{{cite web|last=IBM Corporation|title=DPD chronology|date=23 January 2003 |url=http://www-03.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology2.html|archive-url=https://web.archive.org/web/20100820215557/http://www-03.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology2.html|url-status=dead|archive-date=August 20, 2010|accessdate=September 13, 2012}} The 1009 used the Synchronous transmit-receive (STR) protocol to transfer data at 150 characters per second (cps){{cite book|last1=Pugh|first1=Emerson W.|last2=Johnson|first2=Lyle R.|last3=Palmer|first3=John H.|title=IBM's 360 and Early 370 Systems|year=1991|publisher=MIT Press|isbn=0-262-16123-0|url=https://archive.org/details/ibms360early370s0000pugh|url-access=registration}}{{rp|p.577}} over a single point-to-point dial or leased telephone line. The system was advertised as being able to "link the magnetic core memories of IBM 1401 computers over telephone lines."{{cite journal|title=Data processing magazine|year=1961|volume=3}}

The 1009 attached to IBM 1400 series computers such as the 1401{{cite book|last=IBM Corporation|title=IBM 1401 System Summary|year=1964|url=http://www.textfiles.com/bitsavers/pdf/ibm/14xx/A24-1401-1_1401_sysSummary.pdf|access-date=2012-09-13|archive-date=2011-02-08|archive-url=https://web.archive.org/web/20110208125610/http://www.textfiles.com/bitsavers/pdf/ibm/14xx/A24-1401-1_1401_sysSummary.pdf|url-status=dead}}

In 1961 the transmission rate was doubled to 300 cps.

In 1962 the 1009 was part of a test of data communications using the Telstar satellite to link two 1401 computer systems.{{cite web|last=IBM Corporation|title=IBM and Telstar|website=IBM |date=23 January 2003 |url=https://www.ibm.com/ibm/history/exhibits/space/space_9208ph11.html?fbclid=IwAR3EMFHZOCSQ7mxlEpBMCvfpS_zVEVpof9qWeTWtKa14GUomciwRIdLB5kY|accessdate=November 8, 2021}}