N-1 CARRIER TELEPHONE SYSTEM 445 



Thermal insulation and a thermostatically controlled vent damper limit 

 the temperature range inside the cabinet to approximately 0°F to +150°F 

 for an outside temperature range of — 30°F to +120°F. The temperature 

 range within the cabinet would otherwise exceed that at which it is prac- 

 ticable to operate apparatus components and insure good performance. 

 This type of temperature control is necessary since power is not available 

 for operating either a blower or a heater. 



At a power supply point, a power distribution panel is required for each 

 four systems. This power distribution panel contains the power resistors, 

 fuses and fuse alarm circuits for four local repeaters and four adjacent 

 repeaters in each direction. Other equipment that may be furnished in such 

 an office on a miscellaneous basis is the deviation equalizer panel and the 

 artificial lines required to build out very short spans. The relay rack lay- 

 outs may be arranged in a number of ways to suit the particular installa- 

 tion since no shop wired bays are used. The installation effort is minor 

 since very little wiring is involved. A typical 11-foot 6-inch relay rack lay- 

 out at a power supply point will provide for 16 repeaters including some 

 space allowance for miscellaneous equipment. 



Testing and Maintenance Features 



Potentiometer controls and test terminals are furnished in the various 

 plug-in units for line-up and trouble localizing purposes. In the case of a 

 channel unit, certain adjustments and tests may be made without removing 

 the unit from its frame mounting while others can be made only following 

 the removal of this unit. If removal is required, a multi-conductor test 

 cord provides the means for reconnecting the removed unit to its connector 

 in the frame mounting thereby providing access to test terminals and con- 

 trols within the unit. Also at the terminal office, a portable group unit 

 switching set permits substitution of an alternate transmitting or receiving 

 group unit for the regular group unit without interrupting service. When 

 the removal of a repeater is necessary, it is similarly accomplished without 

 service interruption by the use of a portable repeater switching set. Both 

 switching sets facilitate tube replacement. Two portable tube test sets have 

 been designed for inservice testing of cathode activity of tubes in repeater 

 and group units. An additional repeater test set is used in system line-up 

 and maintenance adjustments. 



A portable maintenance center test set has been designed for use with 

 N-1 carrier equipment. This set is capable of testing and adjusting all 

 equipment units, and the two portable switching sets. The test set is es- 

 sentially a device for interconnecting oscillators, measuring equipment and 

 the units to be tested. Filters and attenuators are included for controlling 

 test currents. 



