288 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 



Electrical Details of Cable-Terminating Equipment 



The majority of the electrical features of the cable-terminating equip- 

 ment have already been considered. 



Within the cable-terminating box (Fig. 4) are the power-separating 

 filters; the high-pass filters CI, C2 and LI passing the carrier frequencies 

 and the low-pass filter L2 passing the direct current. The transmission 

 equipment represented by the block SI is for convenience mounted in the 

 cable-terminating cubicle. The extra low-pass filter L3, C3 can be spe- 

 cially designed to prevent signals that are peculiar to the site (local radio 

 stations, etc.), which are picked up in the power equipment, from being 

 fed to the transmission circuits. 



Metering facilities (not shown in Fig. 4) are provided to check the 

 continuity of the sea-ground circuit. A separate insulated wire is con- 

 nected to the sea-ground plate and the continuity is checked by measur- 

 ing the voltage drop along the ground cable. Aural and visual alarms 

 are given if the sea ground becomes disconnected. 



Current and Voltage Recorders 



Current and voltage recorders are provided for both the regular and 

 the alternate eciuipments, the values being measured at the points where 

 the outputs of the power equipments enter the cable-terminating equip- 

 ment. 



A magnetic-ampUfier unit drives the current recorder, the scale de- 

 flection being from —5 per cent to +5 per cent of the normal line cur- 

 rent. The voltage recorder is connected across the ground end of a resist- 

 ance potentiometer, the full-scale deflection being 3 kv. 



The magnetic amplifier and potentiometer units are mounted in the 

 cable-terminating equipment, but the four recorders and their associated 

 supplies and alarms are mounted on a separate rack. 



Mechanical Details 



Fig. 6 shows two power equipments and a cable-terminating equip- 

 ment as installed at each terminal station. The same cubicle frameworks 

 are used for power and cable-terminating equipments, the power equip- 

 ment consisting of two cubicles bolted side by side and fitted with doors 

 at the front and back. 



The top of the cable-terminating cubicle contains the power-change- 

 over box, the center contains the cable-terminating box, while the trans- 

 mission and ground-cable test circuits are located near the bottom. The 



