TRANSATLANTIC CABLE POWER SYSTEM 161 



Crosstalk and Outside Interference 



111 order to meet the severe crosstalk requirements between receiving 

 and transmitting circuits and to guard against feeding office noise po- 

 tentials into the carrier transmission system, arrangements were made 

 so that office grounds are carefully separated from the outer conductor 

 of the cable and from all circuit elements within the power separation 

 filter. Pickup of external radio-frequency fields by the power separation 

 filters was greatly reduced by completely enclosing in a copper shield 

 the cable terminal and the power separation filter elements nearest to 

 the terminal. The shielding itself and the cans of PSF capacitors and 

 oil-filled coils are connected to the return tape of the cable which is 

 insulated from office ground until it reaches sea water, thus reducing the 

 coupling to the other cable as compared to tying both tapes together at 

 the office or bay frame ground. 



Protection of Personnel 



A key locking system is provided to safeguard against any hazard to 

 personnel from high voltages. In the common bay, the high voltage com- 

 partment can be entered only by operating a switch which shorts the 

 cable to ground and releases a key for the compartment doors. In each 

 regulating bay, the key system assures that the bay is disconnected from 

 the cable and hence from the paralleling power supplies. Where access 

 is required to the interior of any compartment, the key system insures 

 that the ac power to the bay also be switched off. 



The test compartment contains pin jacks, provided for maintenance 

 operations which are always performed with the regulator bay con- 

 nected to a low resistance load. Access to this compartment can be ob- 

 tained with ac power connected to the bay. However, for such access, 

 the key system enforces the operation of the output disconnect switch, 

 which also transfers the bay to a low-resistance load. Moreover, a me- 

 chanical interlock with the autotransformer assures that the test voltages 

 are reduced to safe ^'alues. 



In addition to its function in protecting personnel, the key system 

 also insures that no more than one regulating bay is disconnected at one 

 time so that continuity of service is protected at all times by two parallel 

 regulators. 



FACTORY AND SHIP CABLE POWER 



In addition to the above cable power supplies at the ocean terminals, 

 similar dc cable current regulating equipment was designed for use at 



