152 
NAT ORE 
[APRIL 9, 1914 
The attenuation constant of the line is thus reduced 
to less than half of that of the unloaded line, and 
good speech is possible from New York to Denver. 
It is the ambition of Mr. Vail, the president, and 
Mr. Carty, the able engineer of the above company, 
to complete a loaded line such that speech will be 
possible from New York to San Francisco, a distance 
of more than 3000 miles. Another long loaded aerial 
line just completed is that from Berlin to Rome. 
This line, with the exception of a short piece of cable 
through the Simplon Tunnel, is an overhead line of 
phosphor-bronze, 4-5 mm. in diameter. It is loaded 
every ten kilometres with loading coils having an 
inductance of 0-2 henry. It runs from Rome to Milan, 
thence to Iselle, then through the Simplon Tunnel to 
Brieg, then to Bale and Frankfurt, and so to Berlin. 
TaBLe I. 
Loaded Aerial Land Lines. 
All values are per mile or per kilometre at 800 
frequency. 
| London (St, Albans) 
Tine New York | Berlin and|Berlin and) and Leeds Trunks 
and Denver Rome Frankfurt | SatSS|=—_ 
| No.6 No. 7 
Length + 2000 miles 2082 kms. | 584 kms. 189 miles | 189 miles 
Coil Spacing... 8 miles 1o kms, 5kms. | 8miles | x12 miles 
Coil Resistance) 65 ohms. | 5 87 6°6 4°70 
Total Resist- | 
tance ... 4°95 ohms. 2°9 11°18 7°58 7°08 
Capacity in, 
mfds. ... 000g 070055 0°0055 o’c098 = |S(o'0008 
Inductance in | 
henrys | 010365 0.022 0°0461 0°037 0'0173 
Attenuation 
Constant 00013 O‘ooIET | o*o0org 0°00283 0°00372 
Total Attenua- 
; tion moo 2°6 2°2 1°12 °'55 o'72 
Conductor ... | Copper | Phosphor 
| Bronze Bronze Copper 
Weight or Size 435 1b. to | 4°5 mm. | 
| mile diameter 2°5 mm. 300 lb. to mile 
| diameter 
Dr. Bon and Dr. di Pirro, who have had the charge 
of the scientific work in connection with it, find the 
actual attenuation is closely in accordance with the 
predicted value, and good speech is possible over the 
whole distance. 
In our own country the longest loaded lines are two 
trunk lines running from London to Leeds, 200 miles, 
which are loaded every eight and twelve miles. 
The engineer-in-chief, Mr. Slingo, states that the 
General Post Office has now in operation 30,000 miles 
of aerial and underground loaded circuits, using 12,448 
loading coils; also 45,645 miles more are in course of 
being loaded, so that before long the G.P.O. will 
have 75,000 miles of circuits loaded with 30,000 coils. 
In the United States up to 1912 there were 103,000 
miles of loaded circuits in all. 
In England one of the longest loaded underground 
lines is that from Hull to Newcastle vid Leeds, 154 
miles in length, which is loaded every 2-5 miles. The 
Post Office has now under construction an under- 
ground loaded line from London to Liverpool vid 
Birmingham, which will contain fifty circuits, and 
render communication independent of storms. In the 
United States a long underground line has been con- 
structed from Boston to Washington, 475 miles, pass- 
ing through New York, Philadelphia, and Balti- 
more. A loaded line underground from Berlin to 
Cologne is in contemplation. 
Turning then to submarine cables, we find that at 
present the General Post Office has three such loaded 
cables, one from England to France, laid in 1910, one 
from England to Belgium, laid in 1911, and one from 
England to Ireland, laid in 1913 (see Table IJ.). An 
NO. 2319, VOL. 93] 
= 
Anglo-Dutch cable of the same type is being manu-: 
factured to-be laid between a point in Suffollk and 
the nearest point on the coast of Holland, a distance 
of 125 miles. 
rae Tas_e II. 
Loaded Submarine Telephone Cables. 
All values are per nautical mile of loop at 800 
frequency. 
= Fs| ral | 
S 2 a 
= hse ‘toe 5 ates 
7 =e SOUTH | woe | EUR 
Cable m ge msng] mee see 
Geen | Bas 6 6.5 Holt 
ae Lao 22H ONT 
88 [88.2] BAO 18s 
< < <a < 
Length in nauts = acc 2 48 48 64 
Coil Spacing in nauts ... oer I I I ie 
Coil Resistance in chms, tes 6°6 II's 4°6 68 
Total Resistance in ohms, 20°9 25°7 are7 21'0 
Capacity in mfds. 0°138 o*162 O°314 0166 
Inductance in eas o'r o'r 0°05 o'r 
Ratio S/C wae : I20 I2 12 12 
Attenuation Constant . 0017 o'o18 0°0173 o'CI5 
Total Attenuation 0°36 0°86 0°83 0°96 
Conductor weight per naut 160 lb. 160 b 320 |b. r€0 |b, 
The Anglo-French uniformly loaded cable has an 
effective resistance of 8-54 ohms at 1000 frequency, a 
Wire-to-wire capacity of 0-176 mfd.,- an inductance 
of o-0135 henry, and an attenuation ‘constant 0-0185. 
The total attenuation is 0-39,, the value of S/C is 
109, and the conductor weighs 300 lb. to the nautical 
mile. 
These cables were all constructed by Messrs. 
Siemens Brothers with the cylindrical coils above- 
mentioned. The Anglo-French and Anglo-Belgian 
were laid under the direction of Major W. A. J. 
O’Meara, C.M.G., when engineer-in-chief of the 
General Post Office, and the Anglo-Irish cable under 
Mr. W. Slingo, now holding the same position. The 
French Government also laid from France to Eng- 
land a uniformly loaded cable made by the Telegraph 
Construction and Maintenance Company, which has 
a copper core of twice the weight of the Anglo-French 
cable, and is loaded by being” uniformly wound over 
with one layer of soft iron wire. Each of these cables 
contains two pairs of wires which can be used as two 
independent circuits, and also by using each pair 
conjointly, as a lead and return, can be used to make 
a third or. phantom circuit. These cross-Channel 
loaded cables have enabled telephonic speech to be 
transmitted from London to Geneva, London to Ber- 
lin, and to cities in the south of France. 
Broadly speaking, we can say that by loading cables 
and lines it has been possible to double or more than 
double the distance of effective telephonic intercourse, 
and to speak for 2000 miles overland, 500 under- 
ground, and up to too miles or more under sea. 
It is possible that submarine communication in this 
manner may be increased to 150 or even 200 miles, 
and overland to 3000 miles. 
Turning then to the question of the abolition of 
the line by so-called wireless telephony, Dr. Fleming 
gave a brief description of the apparatus used. The 
arrangements are closely similar to those employed in 
wireless telegraphy. At the transmitting station there 
must be an antenna in which continuous oscillations 
are set up by a Marconi disc generator, a Goldschmidt 
alternator, or some form of are generator, such as 
that of Poulsen or Moretti. 
In the base of the antenna, or coupled to it, must 
be placed a microphone by means of which the 
speaker’s voice makes changes in resistance of the 
antenna circuit. The continuous electric waves 
radiated must have a wave-length of not much greater 
than five or at most ten miles. If a spark system 
