GB711323A - Improvements in or relating to electrical recording apparatus - Google Patents

Abstract

711,323. Recording apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. April 1, 1953 [Aug. 15, 1952], No. 20625/52. Class 106 (4). [Also in Group XXXVIII] An electro-sensitive recording apparatus suitable for use in conjunction with echo sounders and other cyclically operated devices includes means for automatically changing in successive cycles of operation the effective sensitivity of the recorder, the changes of effective sensitivity being themselves repeated cyclically. It is stated that dry electro-sensitive recording paper will give a density of indication proportional to the applied current over a range of about 6db other factors being constant but that graduations in density corresponding to current variations of 14 db or more are desirable for echo sounding records. The present invention is arranged to provide a greater range than the normal 6 db and the embodiment described comprises a recorder whose sensitivity is changed between two values at the end of each cycle of operation. It is shown with reference to the graphs of Figs. 1 and 2 (not shown) that the apparent mark density can be made proportional to the applied current over a greater range by this means. A stylus. on the end of an arm 4 is rotated to pass across the slowly moving recording paper 5 once during each cycle and contacts 3 operated by cam 2 on the driving shaft are arranged to trigger the echo sounding transmitter of equivalent device when the stylus crosses the zero line on the paper. Shaft 1 drives through gearing 7, 8, a shaft 9 rotating at half speed and carrying a cam 10 which closes contacts 11 for one rotation of the stylus and opens them for the next. When closed the contacts short circuit resistor 12 in the cathode circuit of variable Á amplifying valve 14 in the echo sounding receiver. The change of gain should preferably be made equal to the tone range of the paper that is about 6 db.