3400 Hz. Basic speech energy Emotion Frequency (Hz) Figure 5.1 Energy and emotion distribution of human speech. (From BSTJ, July 1931.) 5.3 OPERATION OF THE TELEPHONE SUBSET Transmitter 10-dB pad Transmitter Tele- Tele- phone phone P2 Output in 6 cm³ coupler Receiver Receiver Short loop 1000 ft 26 AWG Long loop 15,000 ft 26 AWG Frequency (Hz) Figure 5.2 Comparison of overall response of the North American 302 and 500/2500 telephone sets. (From W. F. Tuffnell, 500-Type Telephone S, Bell Labs Record, September 1951, copyright 1951 Bell Telephone Laboratories.) Note: The 302 type subset is now obsolete. Figure 5.2 shows the overall frequency response of a simulated telephone network using the standard 500/2500 North American telephone subset. 5.3 OPERATION OF THE TELEPHONE SUBSET A telephone subset consists of an earpiece, which we may call the receiver; the mouth- piece, which we may call the transmitter; and some control circuitry in the telephone cradle-stand. Figure 5.3 illustrates a telephone subset connected all the way through its subscriber loop to the local serving exchange. The control circuits are aptly shown. The hook-switch in Figure 5.3 (there are two) are the two little "knobs" that pop up out of the cradle when the subset is lifted from its cradle. When the subset is replaced in its cradle, these knobs are depressed. This illustrates the "on-hook" and "off-hook" functions described earlier. The "dial-switch" represents the function of the telephone dial. It simply closes and opens (i.e., makes contact, breaks contact). If a 1 is dialed, there is a single break and make (the loop is opened and the loop is closed). When the "loop is closed," Telephone set switch -switch ringer switch Subscriber's premises Outside plant Switch (exchange) Figure 5.3 The conventional telephone subset. Note the hook-switch and dial-switch "controls." 5.4 SUBSCRIBER LOOP DESIGN current flows; when open, current stops flowing. If, for instance, a 5 is dialed, there will be five break-and-make operations which represent the d