Coi
་་
J
18
A
bong Kong Regn. No. 4:35.2.Item No.!!.....
Be
110
SPECIFICATION
——
for
DRY CORE UNDERGROUND TELEPHONE CABLES.
* 2
101.
"
types of
ables.
Armouring.
Cables.
1. The underground cables are to be to the
latest specification of the British Post Office for twin wires, each weighing 10 pounds per mile, paper
insulated and lead oovered.
The electrostatic capacity of each wire measured
against all the remaining wires of the cable and the
lead sheathing must not exceed 0.115 microfarad per
mile. The maximum resistance per statute mile at 60
degrees Fahr. to be 87.825 Standard ohms. The insula-
tion resistance of each wire from every other wire in
the cable and from the lead aheathing, must not be
less than 5,000 megohme per statute mile, after one
minute's electrification at a temperature of not leas
than 50 degrees Fahr. when tested with an E.M. F. of
not less than 300 volts.
2. The armoured cable is to be protected outside
the lead sheath by the following coveringe :-
(a)
Two strips of canvas, each 2 inches wide,
saturated with Stockholm tar and ozokerite
composition, to be evenly laid on in reverse
lay, the first strip to completely cover the
lead, and the second strip to completely cover
the first.