EQUIPMENT FOR MINING, OIL AND CHEMICAL INDUSTRIES
INTRINSICALLY SAFE TABLE TELEPHONES
AUTO TYPES N1882B, N1883A
Certificates T/TEL/89 (Methane), No. 112 (Pentane)
Type N1882B shown
The need for a modern desk telephone for colliery offices has led to the development of this intrinsically safe version of the Etelphone, which is not only more convenient than the wall instruments in current use but also has the technical and mechanical advantages of the standard Etelphone.
Types N1882B and N1883A are identical except that the latter includes an Operator Recall push-button, whilst the former has a dummy button.
The instrument is for use in offices in collieries, oil installations and similar hazardous conditions such as chemical works and docks.
It is approved for pit-bottom offices when connected to the Mine P.A.X. or P.A.B.X. via an E.T.L. Safe Link Unit located above ground; it is not suitable for installation in Mine roadways.
The telephone has a tough moulded plastic baseplate on which all the apparatus is mounted, and a high-impact-resistant black plastic drop-on case which is attached to the baseplate by two screws under the handset. The case can be removed without inverting the instrument or preventing its working. A chrome carrying-handle is fitted under the handset, which is light in weight, made from the same material as the telephone case, and so shaped that the natural grip positions the mouthpiece correctly for maximum transmission efficiency.
The dial numbers, being external to the dial, are unobstructed and cannot be defaced as they are on the underside of the number ring. The push-button (or dummy button) is above the dial.
Non-slip feet are attached to the telephone baseplate.
OPERATIONAL EFFICIENCY AND APPARATUS
The exceptional frequency response and volume efficiency of the instrument are largely due to the use of a highly efficient antiside-tone induction coil and a rocking-armature receiver. For colliery applications the loop resistance between the telephone and link must not exceed 300 ohms.
All components are of proven reliability. The risk of low-insulation faults in connecting wires and cords is minimised by the high grade p.v.c. insulation, which is impervious to moisture, fire-resistant, and not subject to attack by insects or mould growth.
The extensible handset cord is p.v.c. insulated.
External wires connect to screw terminals in a moulded desk terminal block which is connected to the instrument by a 4-way p.v.c. insulated straight cord. Terminals for a Type N3130A extension bell are included in the desk block.
The stock telephone is black and is suitable for use in the tropics.
The dial has a 2:1 break-make pulse ratio and a speed of 10 i.p.s. unless otherwise ordered. Marking on the number ring can be modified to customer's requirements.
Specify the telephone Type No., and Extension Bell N3130A if required.
|N1882B||Auto table set without button||3 lb. 11 oz. (1.67 kg.)|
|N1883A||Auto table set with button||3 lb. 11 oz. (1.67 kg.)|
Taken from the Ericsson Catalogue No. 60
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