PLANNING AND OVER-ALL PERFORMANCE 21 



to avoid transmission degradation, it was agreed that the signahng 

 power and duration would not amount to more than 9 milliwatt-seconds 

 in the busy hour at a zero level point; this would not contribute unduly 

 to the loading of the system. 



It was agreed that, for initial operation, ringdown signaling would be 

 employed, but the system design should be such as to permit the use of 

 dialing at a later date. 



Echo Suppressors 



Echo control was considered essential, since the via net loss of the 

 transatlantic circuits would be only 0.5 db, with a one-way transmission 

 time of 35 milliseconds. Echo suppressors would be provided initially at 

 New York and Montreal only, and arrangements made in London to 

 cut out such suppressors as may be fitted there on Continental circuits, 

 when these are used for extension of the transatlantic circuits. It was 

 recognized, however, that other suppressors might be encountered in the 

 more remote parts of Continental and United States extensions. The 

 general problem of how best to arrange and operate echo suppressors on 

 very long switched connections is one which remains for consideration 

 later. 



Maintenance and Operating Services 



Telephone Speaker and Telegraph Printer Circuits 



The need for telephone and telegraph circuits for maintenance and 

 administration was recognized, and it was agreed to provide the fol- 

 lowing circuits on the submarine links at frequencies immediately out- 

 side the main transmission bands where inferior and somewhat uncer- 

 tain characteristics might be expected (Fig. 4) : 



(a) A 4-kc band, possibly sub-standard in regard to noise, equipped 

 with band splitting equipment (EB Banks) to provide two half-band- 

 width telephone (speaker) circuits, and 



(b) two frequency-modulated telegraph (printer) circuits. 



These circuits would be extended over the land circuits to the terminal 

 stations by standard arrangements as needed and would be used to pro- 

 ^'ide the following facilities: 



(I) An omnibus speaker circuit connecting the principal stations on 

 the route, including Montreal. 



(II) A speaker circuit for point-to-point communication between the 

 principal stations — i.e., non-continuous. 



(III) A direct printer circuit between London and White Plains. 



(IV) An omnibus printer circuit as (I) above. 



