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Section 2-- Communications Background
Pages 15-20

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From page 15...
... to other central offices nearby; or (b) extending into the to11~te1ephone network, The Te1eph6ne The user interfaces with the telephone system at the telephone instrmnent, From the network~contro1 viewpoint, the user performs as a highly adaptable logic and memory system that responds to incoming calls, initiates calls, and reacts reasonably predictably to a variety of situations encountered in using the telephone, The mechanisms he uses to exert this control in the simplest form of telephone are the switch hook and the dial, Lifting the handset closes electrical contacts in the switch hook to signal the central office.
From page 16...
... It contains nonlinear devices that limit energy levels, particularly on short loops to the central office. Where the user telephone system is replaced by a machine, with or without interfacing equipment, the three basic functions of network control,
From page 17...
... To hold cross talk between services carried over these pairs to a minimum, there must be strict control in cable manufacture to avoid structural imbalance. The effect of this careful control can be destroyed if improperly designed or improperly installed equipment is connected to the ends of the pairs.
From page 18...
... Since these switches are mechanical devices with definite speed limitations, the dial-return mechanism is equipped with a speed governor, as a kind of buffer against an impatient user. In common-control offices, operation of the dial controls the condition of groups of relays or solidstate electronic circuits, which are made available for the user's sole use, when he gets a dial tone.
From page 19...
... The total available load capacity of the amplifiers are designed to be shared evenly by all the channels, whether they are handling voice or other communications. Specifications for individual channel loading have been established to be an optimum comprise between low levels where underlying system noises dominate and the higher levels where intermodulation noise and cross talk prevail.
From page 20...
... i only are provided -~ the user attaches his own equipment, I Touch-Tone Services There are over 1,000,000 telephone installations in which the rotary dial has been replaced by a 10- or l2-button "touch-tone" combination. The touch-tone signals, unlike the rotary~dial signals, can be used, not only to control the setting up of the connection, but also to transmit data once the connection has been set up,

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