| 摘要 |
965,418. Telephone transmission systems. WESTERN ELECTRIC CO. Inc. Oct. 18, 1960 [Oct. 30, 1959], No. 35663/60. Heading H4R. In an arrangement in which supply currents are fed over the signal path and are separated at an amplifier, inductance means are included in the inputs and outputs of the amplifier, each means having two coils, both of which are included in the signal path with such polarity as to offer no impedance to the signals, and one only of which is included in the heater circuit so as to offer high impedance to stray signal currents entering the heater circuit. Such stray currents have an adverse effect upon the gainfrequency response of the amplifier. As shown, the amplifier 21 is arranged to amplify high frequencies passing from terminals 11 to 16 and low frequencies from terminals 16 to 11, condensers 47, 48 and inductances 49, 50 being symbolical representations of high- and low-pass filters respectively. Signal currents are developed across and emitted from inductances 17, 19 and heater currents are developed across and emitted from condensers 18, 20. Stray capacities between the input and output circuits occur across transformers 51, 52, between transformers 26, 32 and chassis and also across the windings of these transformers. All these capacities are effectively shunted by connections 57, 60 so that now the only effective stray path for these currents is via these connections and the heater circuit; and this path contains the lower windings only of the inductances 53, 56 which present a high impedance. The signal paths contain also the upper windings of these inductances, and are thus unaffected. Condensers 22a, 22b, 40a, 40b provide D.C. blocking and inductances 41, 42 provide high signal current impedance and a path for the heater current. The latter may be omitted (i.e. left open circuit) and condensers 22b, 40b omitted to provide a path for the heater current in this way, if there is no risk of the heater current saturating the inductances 53, 56. |
