Introduction.............................................. 33
Modem rings............................................. 47
[1-A]................................. 52
[1-1]............................. 34
[1-5]............................. 43
[1-6]............................. 45
[1-7]............................. 46
[1-8]............................. 47
[1-9]............................. 48
Introduction .............................................. 55
[2-1] ................................. 56
Introduction .............................................. 63
[3-5] ................................. 65
[3-6] ..................................... 66
[3-9] ................................. 70
Voltage ..................................................... 70
[2-7]............................. 57
[2-A]............................. 61
[3-1]............................. 64
[3-2]............................. 64
[3-3]............................. 65