Evolution of Communication Networks in the 19th Century to Digital Communications

1. Chapter 1 Evolution of Communication Networks

2. 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 ? Contents

3. 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 ? Contents

4. 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. The Morse TelegraphSamuel Morse, 1791-1872 First electrical telegraph demonstrated in 1837

6. 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. The TelephoneGraham Bell, 1876.

8. 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 vs. Digital Analog Digital

9. 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 Digital Techniques

10. 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 ? Contents

11. The TelephoneFull mesh network n*(n-1) 2

12. The TelephoneWith central switchboard n

13. Automatic Exchange(1920) Conversation with switch operator replaced by signaling protocol - Voice : analog - Signaling : digital

14. SW Trunk lines SW SW SW SW SW PABX PABX SW The Telephone Network

15. Telex Networks(1930-1990) Morse code replaced by Baudot or ASCII code

16. Morse Baudot ASCII A a B C D E 3 9 Alphabetical Codes

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

18. 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 FFFF = 65537 Unicode (16 bit)

19. The Dual Networks Voice Network Analog+Digital Data Network Digital