| 摘要 |
<p>552,651. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., and FRYDMAN, E. Oct. 15, 1941, No. 13264. [Class 40 (iv)] [Also in Group XXXVII] Alternating current for ringing and tone signalling is derived from a direct current supply by means of a vibratory relay the periodicity of which is determined by a condenser of large capacity. As shown, the relay RV, which is slugged to retard its operation and release, is maintained after its contact rvl opens over both windings in series until the condenser Cl is fully charged. When the contact recloses, the operation of the relay is delayed by the discharge of the condenser through its lower winding. The condenser may have a capacity of the order of 2 mf. The relay may have a single winding only, the condenser C1 and resistance R1 being shunted across the contact rvl. At contact rv2, the relay energizes alternately the opposite halves of the centre-tapped primary of a transformer TR in series with a choke I. Resistances R2, R3 and condensers C2, C3 serve for spark-quenching and smoothing.</p> |
