MULTIPLEX TELEPHONY AND TELEGRAPH Y—SQUIER. £37 
is 5.4 ohms at 100,000 cycles. This would require a capacity of 
about 0.3 microfarad for resonance at this frequency, but in the 
experiments conducted at 100,000 cycles it was found necessary to 
decrease this amount on account of the fixed auxiliary inductance of 
the leads. 
CONSTANTS OF THE TELEPHONE LINE. 
The telephone line used in these experiments extends from the 
Signal Corps laboratory at 1710 Pennsylvania Avenue to the Signal 
Corps research laboratory at the Bureau of Standards. 
This line is made up of the regular standard commercial equipment 
and consists of paper-insulated, twisted pairs in lead-covered cable, 
placed in conduit in the usual manner employed for city installation. 
For the sake of convenience, one of the pair is designated as No. 1 
wire and the other as No. 2 wire. 
The air-line distance between the two laboratories is a little over 
3 miles (4.8 kilometers), but the telephone line, by passing through 
three exchanges, covers about 7 miles (11.27 kilometers). The course 
of the line, with the size and type of conductor, is as follows: 
Laboratory to main exchange, underground cable, No. 22 B. & S. 
Main exchange to west exchange, underground cable, No. 19 B. & S. 
West exchange to Cleveland exchange, underground cable, No. 19 B. & S. 
Cleveland exchange to Bureau of Standards, underground cable, No. 19 B. & S. 
All underground cable except from Bureau of Standards to Wisconsin Avenue and 
Pierce Mill Road, about 3,400 feet, which is aerial cable. 
This line is equipped with protective heat coils of a standard type, 
one in each wire of the metallic circuit, at the Cleveland exchange and 
the main exchange, but none at the west exchange. The constants of 
each of these coils are as follows: 
Mirecieurteat resistances oF 65° IO A OR IOY, ee ohms')** 558 
Size of wire, No. 30 B. & S. 
Pen GEWITR 2. ssa oy Eb args etn giiy- hansen ds? sit siewesesr 3 cm... 40 
PER eTOL LEAS imHeACh COM -ADOUG. eS EO ee te 38 
Measured inductance:at 70,000 eycles.. 2.2922 2S 22g ee bs ke em.. 4,400 
Or 4.4X10~ henry. 
The above constants were measured from a sample of one of these 
coils selected at random. 
einianeei GL metallic CLC icf. 42) Pasig. f2- be. gered ses ot HaGe ohms.. 776 
Capacity measured (one minute electrification) between No. 1 and No. 2 wires 
mal SS A OE Re aE ae es ea ON alten See ee a ee te microfarad.. 0. 69 
Insulation resistance: 
Between No: P wire and earth: J)... 222.202 20272) i222). ..2.megohms.: 009 
Between No. A svireand(earthuyp rast: Os. Same st LOLLOe .edeaIA Vas 
Between No. 1 and No. 2 wires in parallel and earth...............-. do.... 0.8 
Botween No, ang No. 2 witeses 2860 oc occ b a aw nen = eee MOgee yen 
The line included the usual house-wiring at each station, which was 
undisturbed in taking the measurements. 
