| 摘要 |
<p>683,995. Automatic exchange systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Dec. 28, 1950 [Dec. 31, 1949], No. 31486/50. Class 40 (iv). In a circuit in which free and busy outlets are distinguished by potentials, a quick acting test relay T is disabled over a rectifier g at busy outlets but pulls up at free outlets and applies a higher potential to its winding so that the outlet under test acquires a busy potential marking. As shown, a selector S previously positioned by dialled impulses hunts for a free outlet under the control of a rotary magnet D. Busy outlets have a potential of - 6.8 volts and point P on a potentiometer R1, R2 a potential of - 10 volts so that rectifier g is cut off. A free outlet initially exhibits battery potential of - 60 volts but acquires a temporary busy marking potential of - 9.2 volts when the test relay responds so that the outlet is immediately marked busy to other switches. The test relay disables relays D and TT to stop the switch and disconnect the potentiometer. A slow-acting differential relay C individual to the outlet then pulls up over winding C1 and inserts a resistance R3 which changes the outlet potential to a final busy value of - 6.8 volts. In the next switching stage (not shown), an off-normal contact k connects relay winding C2 in parallel with T. At the completion of the call, a busy relay (not shown) opens contacts h1, h2 and relays T and C restore to normal. Suitable ohmic values of the resistances and relay windings to provide the stated potentials are given in the Specification.</p> |
