UN CIRCUITO DE ADAPTACION DE IMPEDANCIAS DE UN APARATO DE ABONADO TELEFONICO

摘要

In a telephone instrument line output circuit an impedance (R1) is connected in series with the line. A negative impedance, e.g. provided by an AC positive feedback loop to the output stage (TR1) is connected in parallel with the impedance (R1). The line therefore 'sees' the parallel combination of these two impedances. This allows a relatively low value of the impedance (R1) to be employed thus increasing the line power available for operation of the instrument and enabling the instrument to meet the administration specification.