1. Postacademic Interuniversity Course in Information Technology – Module C1p1 Chapter 1 Evolution of Communication Networks

2. Postacademic Interuniversity Course in Information Technology – Module C1p2 Contents The 19th century telecommunications –Telegraph - Telephone –Digital vs. analog communications The voice networks & the data networks The electronics revolution (1960-1980) –Digital sound –Mainframe computers with remote access –The first unification : ISDN –Local area networks –Wide area and local area networks integration The Internet –The research project –The universal computer communications medium –The successful unification ?

3. Postacademic Interuniversity Course in Information Technology – Module C1p3 Contents The 19th century telecommunications –Telegraph - Telephone –Digital vs. analog communications The voice networks & the data networks The electronics revolution (1960-1980) –Digital sound –Mainframe computers with remote access –The first unification : ISDN –Local area networks –Wide area and local area networks integration The Internet –The research project –The universal computer communications medium –The successful unification ?

4. Postacademic Interuniversity Course in Information Technology – Module C1p4 The Chappe Telegraph (Claude Chappe, 1763-1805) 92 out of 256 (= 4*8*8) positions represented characters. Integrity of message could be restored at each relay station In 1844, 534 relays linked Paris with 29 cities, covering in total 5000 Km.

5. Postacademic Interuniversity Course in Information Technology – Module C1p5 The Morse Telegraph Samuel Morse, 1791-1872 First electrical telegraph demonstrated in 1837

6. Postacademic Interuniversity Course in Information Technology – Module C1p6 The Morse Telegraph Signal strength can be restored by means of electromechanical relays connecting separate telegraphic circuits. On land lines, unlimited distances can be covered, without increasing significantly the error rate.

7. Postacademic Interuniversity Course in Information Technology – Module C1p7 The Telephone Graham Bell, 1876.

8. Postacademic Interuniversity Course in Information Technology – Module C1p8 Analog vs. Digital Almost infinite number of states External perturbations can not be distinguished from original signal (superposed noise) Information degrades along the lines Finite, small, number of states Most external perturbations can be distinguished from original signal Information can be restored in relays 6:12 Analog Digital

9. Postacademic Interuniversity Course in Information Technology – Module C1p9 Digital Techniques Representation of numbers in electronic devices ? Binary numbers (base 2) are used. A binary digit (bit) can be represented by a switch: –Value 0 : switch open –Value 1 : switch closed A number with n bits can take 2 n different values –2 bits : 4 combinations 00 01 10 11 –3 bits : 8 combinations 000 001 010 011 100 101 110 111 –8 bits (= 1 byte) 256 combinations –16 bits: 65 536 combinations –24 bits: 16 777 216 combinations –32 bits: 4 294 967 296 combinations

10. Postacademic Interuniversity Course in Information Technology – Module C1p10 Contents The 19th century telecommunications –Telegraph - Telephone –Digital vs. analog communications The voice networks & the data networks The electronics revolution (1960-1980) –Digital sound –Mainframe computers with remote access –The first unification : ISDN –Local area networks –Wide area and local area networks integration The Internet –The research project –The universal computer communications medium –The successful unification ?

11. Postacademic Interuniversity Course in Information Technology – Module C1p11 The Telephone Full mesh network n*(n-1) 2

12. Postacademic Interuniversity Course in Information Technology – Module C1p12 The Telephone With central switchboard n

13. Postacademic Interuniversity Course in Information Technology – Module C1p13 Automatic Exchange (1920) Conversation with switch operator replaced by signaling protocol - Voice: analog - Signaling: digital

14. Postacademic Interuniversity Course in Information Technology – Module C1p14 The Telephone Network PABX SW PABX SW Trunk lines

15. Postacademic Interuniversity Course in Information Technology – Module C1p15 Telex Networks (1930-1990) Morse code replaced by Baudot or ASCII code

16. Postacademic Interuniversity Course in Information Technology – Module C1p16 Alphabetical Codes

17. Postacademic Interuniversity Course in Information Technology – Module C1p17 ASCII Character Set (7 bit) 000 001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 ! “ # $ % & ‘ ( ) * +, -. / 048 049 050 051 052 053 054 055 056 057 058 059 060 061 062 063 0 1 2 3 4 5 6 7 8 9 : ; < = > ? 064 065 066 067 068 069 070 071 072 073 074 075 076 077 078 079 @ A B C D E F G H I J K L M N O 080 081 082 083 084 085 086 087 088 089 090 091 092 093 094 095 P Q R S T U V W X Y Z [ \ ] ^ _ 096 097 098 099 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 ` a b c d e f g h i j k l m n o p q r s t u v w x y z k { | } del 032 033 034 035 036 037 038 040 041 042 043 044 045 046 047 016 017 018 019 020 021 022 023 024 025 026 027 028 029 030 031 nul soh stx etx eot enq ack bel bs ht lf vt ff cr so si dle dc1 dc2 dc3 dc4 nak syn etb can em sub esc fs gs rs us

18. Postacademic Interuniversity Course in Information Technology – Module C1p18 Unicode (16 bit) FFFF = 65537 0000 ASCII Latin,Greek,Cyrillic, and Armenian Arabic and Hebrew Indic Punctuation, math, graphics Chinese / Japanese / Korean symbols Unified Chinese / Japanese / Korean ideographs Private applications

19. Postacademic Interuniversity Course in Information Technology – Module C1p19 The Dual Networks Voice Network Analog+Digital Data Network Digital