332 BELL SYSTEM, TECHNICAL JOURNAL 



periphery. Above the drum and paper are a typewriter ribbon and 

 a thin bar which may be made to come down on the ribbon, paper 

 tape, and spiral wire, by the action of an electromagnet. The action 

 of this striker bar is to cause a dot to be made on the paper strip at 

 the position where the striker bar and spiral wire intersect. The 

 drum carrying the spiral wire revolves in synchronism with the phase 

 shifters and there is consequently a lateral position on the paper 

 corresponding to each one of the 44 condensers previously mentioned. 

 When each condenser is discharged by the action of the vacuum tube 

 voltmeter a dot is made in a particular lateral position on the paper 

 strip and successive dots caused by the discharge of the same con- 

 denser fall in the same longitudinal line on the strip. The frequency 

 of dots in a particular longitudinal line is, therefore, proportional to 

 the relative field strength at a vertical angle corresponding to that 

 line. As a result of the action of the automatic volume control on 

 the monitoring branch amplifier, the maximum frequency of dots 

 along a longitudinal line is kept approximately constant regardless 

 of the absolute value of signal received so that the device does not 

 record the variation of signal at a fixed angle from minute to minute. 



A sample of a section of a record is shown on Fig. 9, together with 

 a scale showing the angles corresponding to the rows of dots for a 

 particular received frequency. The angle record is contained in the 

 section above the "Phase Shifter Position" scale. 



In order to have a check on, and a record of, the operation of the 

 automatic angle adjusting equipment, provision has been made so 

 that three longitudinal lines are drawn on the paper corresponding 

 to the three angular positions of the diversity branches. 



A record of the operation of the automatic delay adjusting device 

 is also made by the recorder. This was done by inserting a mechanism 

 which uses the margins of the paper on either side of the main record. 

 The delay recording device consists of two drums mounted con- 

 centrically with the main recorder drive shaft which are similar in 

 nature to the tens and units drums of an ordinary counter. Flexible 

 shafts extend from the delay adjusting switches to the recorder where 

 they drive the drums on each end of the shaft. The two drums on 

 one end are connected together with an intermittent movement so 

 that one revolution of the small units drum causes the large units 

 drum to move forward one step. 



With the paper tape normally running at only \" per minute it is 

 impractical to stamp numbers on the paper since the delay adjustment 

 varies several times in a minute and thus would cause the numbers to 

 record on top of one another. Recourse was accordingly taken to a 



