STERLING TELEPHONE AND ELECTRIC Co. Ltd
THE STERLING PRIMAX SYSTEM
OF COMMON BATTERY AUTOMATIC INTERPHONES
AN ASSURED SUCCESS
Our Primax Interphones were placed on the market many years ago. The system from it's inception established itself in the confidence of the Electrical Trade and the Public, and its popularity has steadily increased.
It was introduced owing to the excessive amount of induced over-hearing and cross-talk prevalent with all ordinary inter-communication single line and common return systems: in addition to which the central battery and Invicta cell is far more convenient and efficient than the old local Battery System.
We desire it to be clearly understood that we do not put tins system forward as one which will provide a secret-conversation service, but what we do say is that induced cross-talk has been so far eliminated that it is now possible in a system of, say, 20 of our Primax Interphones, to carry on the maximum number of conversations simultaneously without confusion.
When it is appreciated that only two additional common wires are required in the cable, we are convinced that our friends will not be slow to take advantage of thus very desirable innovation.
We particularly draw attention to the fact that all our Battery Ringing Automatic Inter-communication Telephones from U 410 to U 442 will (unless otherwise specified) in future be supplied constructed for our new system, now known as The Sterling Primax System of Automatic Interphones.
All Instruments to work with this System must bear the mark "Primax" System.
Ordinary Leclanché Batteries or Dry Cells must not be used.
NUMBER of CELLS REQUIRED
3 "Invicta" Cells (S 7090a) for the Common Speaking Battery.
3 or more "Invicta" Cells (S7090a) for the Common Ringing Battery according to the size of the installation.
Taken from the Sterling Catalogue No. 12
Last revised: June 30, 2019