Transmitted Frequency Range for Telephone Message Circuits

the Bell System the general objective for INthe transmittedrangejhaving range forofnewwhich hasof been set upfrom frequency designs telephone message circuits is a a width 2,500 cycles, extending about 250 cycles to about 2,750 cycles. In determining the frequency range of such a circuit, the cutoff points are taken as those at which the attenuation reaches a value 10 db greater than that at 1,000 cycles. This frequency range for design is taken in general as applying to the overall transmission characteristic of the circuit between the terminal central offices of a connection. Where such offices are connected by a direct trunk this frequency range applies to the individual trunk. Where two or more trunks are used in tandem the frequency range of the overall connection will tend to be somewhat less than that of the component parts. For this reason then, to meet the specified range for an overall multi-switch connection, it will be necessary to have the frequency ranges of the trunks which are used as parts of built-up connections, somewhat greater than the specified range for the overall circuit. In view of the relatively lower cost of toll switching trunks and other similar trunks from toll offices to local central offices, it is desirable that these terminal circuits have a broader frequency range than that specified above, so as to avoid their narrowing the range transmitted by the toll trunks with which they are connected. It may be stated that the general purpose in working to the transmitted frequency range given above is that each individual trunk should have a frequency range at least as great as that specified and that the frequency ranges of those trunks which are frequently used as parts of built-up connections should be somewhat greater than the specified range.