GB818124A - Improved arrangements for balancing hybrid connections - Google Patents

Abstract

818,124. Impedance balancing networks. STANDARD TELEPHONES & CABLES Ltd. Sept. 13, 1957 [Sept. 14, 1956], No. 28913/57. Class 40 (8). [Also in Group XXXIX] In a hybrid arrangement in which capacitances C1 ... C4 are included in the transformer to form a high-pass filter in order that noise and/or low signalling frequencies may be excluded, the series condenser or inductance of the balancing network is omitted, compensation being effected by modification of the values of the first mentioned capacitances. In Fig. 3 a normal arrangement would be realized if C8 were omitted and a series capacitor C5 (not shown) were inserted in the lower leg of the balance arm. Since this latter condenser is in series with C2 its omission would make the capacity of this arm too large. Compensation is effected by increasing the capacity of the other arm by shunting an additional condenser C8 across C1. In the event that the presence of the line transformer T3 so increases the effective line inductance that a series inductance would normally be required in the balance network, this inductance may be omitted, compensation being effected by connecting the additional condenser across C2. Conventional switching means for connecting C8 across one or other of C1 and C2 is provided. Condenser C8 is small and can thus be easily made of the variable type as is normally required.