531 HYDROGRAPHIC MANUAL PaGE 500 



component parts that constitute the instrument. Graphic recording and the use of 

 supersonic frequencies were pioneered in Europe, with the result that there is a more ex- 

 tensive appHcation of them there. Visual types of echo-sounding instruments are also 

 manufactured in Europe, but are used to a lesser extent. 



531. French Instruments 



A prominent French manufacturer of echo-sounding instruments uses the trade name S.C.A.M. 

 (Soci^te de Condensation et d' Applications M6caniques). Both visual and graphic-recording instru- 

 ments intended for use in navigation and surveying are manufactured. One feature common to the 

 instruments manufactured by this company is the use of high supersonic frequencies produced by 

 means of the piezoelectric properties of quartz crystals. This type of acoustic transmitting and 

 receiving unit is described briefly in 5161C, and is illustrated in figure 98. Electric energy to excite 

 the quartz-crystal transmitting unit is furnished by a low- voltage d-c supply connected to the primary 

 of a step-up transformer. The keying circuit interrupts the current flowing in the primary circuit of 

 this transformer, inducing a high voltage in the secondary circuit. Through appropriate connections 

 this voltage excites a tuned circuit whose frequency is the desired emission frequency. The oscilla- 

 tions set up in this circuit are transmitted to the quartz-crystal transmitter, whose vibrations produce 

 a train of damped acoustic waves in the water. The frequencies of the transmitting and receiving 

 units of the various S.C.A.M. instruments are from 29 to 65 kilocycles. 



5311. Langetin-Touly Electrolitic Recorder 



The Langevin-Touly electrolitic recorder is one of the standard instruments made by S.C.A.M. 

 The depth is recorded graphically on a moist electrolitic paper that passes under a cam-operated stylus. 

 The stylus moves at a uniform radial rate across the paper in an arc from left to right, and returns by 

 a very rapid reverse movement. The acoustic signal is transmitted at the beginning of the left-to-right 

 movement, the echo registering on the paper during this travel. Some of the principal features of 

 this recorder are : 



(a) A depth range from 3 to 300 meters, with successive additional phases of 300 meters each. 



(6) The graduations of the depth scale are marked directly on the fathogram by means of a multi-division brush. 



(c) The use of high supersonic frequency produced and received by quartz-crystal units. 



(d) A recording mechanism operated by a 7-volt motor operated from an 8-volt storage battery. 

 («) A paper speed of 36 inches per hour, one roll of paper lasting 40 hours. 



(/) An attached magnifying glass to aid in scanning the fathogram. 

 (a) A motor speed indication by means of a stroboscope. 



5312. Echometre 



The indicating device of this instrument operates in a manner similar to a string galvanometer. 

 A beam of light falls on a small mirror and the echo voltage operates a,n electromagnet which rotates 

 this mirror through a small angle, causing a vertical deflection of the light beam. After reflection from 

 this mirror, the light strikes another mirror which rotates at a constant rate about a vertical axis for 

 a few degrees in one direction, returning in the opposite direction very rapidly to the starting point. 

 The light reflected from the second mirror falls on a translucent scale which is graduated in fathoms, 

 or meters, or both. The spot of light thus travels from left to right across the depth scale at a constant 

 rate. On reception of the transmitted and echo signals the first mirror deflects this spot of light ver- 

 tically, and at such points the light forms a peak rising above the base line of light, adjacent to the scale. 

 The signal is transmitted at the beginning of the left-to-right travel of the light spot. Some of the 

 features of the Echometre are: 



(o) A sounding range from 3 to 660 meters. 



(6) The use of a high supersonic frequency, the signal being produced and received by quartz-crystal transmitting and receiving 

 units. 



(c) The depth-indicating mechanism, echo amplifier, and high-frequency generating equipment to energize the transmitting unit 

 all in a single cast-metal cabinet. 



(d) The visual indicating device operated by a spring-operated clock motor whose speed is controlled by a governor. 



(e) A ratchet wheel that rotates a mirror horizontally by means of a pawl at a constant rate in one direction and releases the pawl 

 at a determined point to let the mirror and pawl snap back to the starting point. 



(/) Soundings taken at the rate of six every 7 seconds. 



(g) A circuit that permits listening for the echo. 



(A) The type of bottom is approximately indicated by the shape of the echo trace on the indicator. 



