582 BELL SYSTEM TECHNICAL JOURNAL 



Cabling Problems and Floor Plan Layouts 



The floor plan arrangements for type K carrier equipment have been 

 controlled to a considerable extent by transmission requirements, with 

 consideration also being given to satisfactory operating and mainten- 

 ance layouts both for the initial installation and for the future. The 

 first consideration of any space which is to be used for carrier equip- 

 ment is that the various units of equipment can be so located, with 

 respect to each other, that the established maximum wiring lengths, 

 as determined by transmission, operating, and economic requirements, 

 will not be exceeded. For example, the length of shielded pair cable 

 between the jacks in the input sealed test terminal bay and the input 

 side of the line amplifier has been limited to about 50 feet and the 

 potentiometer lead between the voice frequency patching bay and the 

 channel modem units has been kept short in order not to limit the ad- 

 justment range of the potentiometer and a limit of 150 feet has been 

 set. These limits were set in the design of the type K systems. Two 

 types of cabling were installed in the transmission part of the carrier 

 circuit; i.e., standard lead covered cable and shielded pair cable. 



In cabling the carrier equipment the input leads were not run on the 

 same cable racks with voice frequency cables. Due to the difference in 

 transmission level between cabling connected to the input sides of 

 carrier amplifiers and that connected to the output sides, these two 

 groups of cabling have been segregated by running them over separate 

 cable racks. The input leads were spaced not closer than two feet to 

 any leads carrying interrupted direct current or power supply leads 

 which might possibly carry high-frequency noise currents. Output 

 leads were run on the same cable racks with voice frequency cabling 

 where necessary, but were kept six or more inches away from possible 

 disturbing leads such as those just mentioned. Cabling from the 

 voice frequency side of the channel modem equipment was installed 

 without greater precautions than are used when installing other voice 

 frequency cabling. Crosstalk balancing bays were installed in any 

 convenient location without special limitations in the lengths of lead 

 covered cables between these and the input sealed test terminal bays. 



All cable racks carrying the rubber covered shielded cables from the 

 amplifier and group modem bays to the sealed test terminal and high- 

 frequency patching bays were arranged so that these leads were run 

 loosely and without sewing. This arrangement provides a ready 

 means for switching cables for circuit layout purposes, particularly at 

 terminal offices or at junctions of carrier cables. 



In existing offices the high-frequency jack and testing equipment has 

 been located as close as practicable to the existing toll testboard posi- 



