GB584979A - Improvements in or relating to electric attenuators - Google Patents

Abstract

584,979. Electric attenuators. LOWE, A. C. BOWYER-, PEACH, E. R., and PYE, Ltd. Oct. 10, 1944, No. 19443. [Class 40 (iii)] An electric attenuator having a resistance network comprising a number of sections connected in series, each section formed by a series resistance and a shunt resistance and having a switch for selecting one or more sections of the network, is such that the network resistances are enclosed in a metallic casing partitioned by metallic screens to form a series of compartments which house the shunt resistances, and the series resistances are arranged to pass through the screening partitions, but insulated therefrom, so that the ends of each series resistance are disposed in adjacent compartments on opposite sides of the intervening partitioning screen. The compartments 9 are formed by walls 10 extending from a central recessed boss 6 integral with a baseplate 1 and having a wall 5 to which a cover 2 is attached. The series resistances R2 ... R5 pass through open-ended slots which are closed by plates. 14 and their ends are secured to metal clips 12 attached to the wall 5 by insulating blocks 11. The shunt resistances R6 ... R10 have their upper ends attached to clips 18 and their lower ends supported by the surface of recesses 17 in the portion 16 of the base. The clips 12, 18 are electrically connected by contact studs 19 engaged by a curved contact strip 22 mounted on pins 23 on a head 24 rotatable by a spindle 25. The strip'22 is retained in a central position opposite the corresponding stud 19 by spring-pressed balls 33 engaging radial grooves 32 in a metal disc 30 secured to the head 24. The contact strip 22 is connected by a biassing spring 26 and a metal strip 28 to a stud 29 engaging a disc 36 connected by a strip 37 and conductor 40 to one conductor of the output socket 39, the second conductor being connected to the socket and the casing. The contact stud 19 engaged by the strip 22 is screened from other contact studs by a metal screen 31' mounted on the head 24 and arranged to engage the arms of a stop member 34. The input conductors are connected respectively to the casing and to a clip 12a associated with resistances R2, R6 and an alternative position for the input socket 41 is closed by a plug 43. During movement between the studs 19, the pick-up contact 22 is short-circuited to the casing by engagement with the wall 5 under action of the spring 26.