Shipton Inter-Dial telephone system

The Shipton Inter-Dial telephone system is one that often confuses telephone collectors, being visibly a non-standard affair.  In fact it was, as its name suggests, based on a combination of intercom and dial telephone practice.  Conceived by Edward Shipton and launched in 1929, it offered a low-cost internal telephone system that employed a familiar-looking dial instead of the normal push buttons to select the person being called.  That’s where the familiarity ends, however, because the ‘dial’ is not the Dial No. 10 that it resembles, as becomes evident when you disassemble the telephone.  On the rear of the dial is a rotary selector switch, not the normal type of dial mechanism.  To use the dial you simply pull the finger wheel around to the single-digit number required.  There is no spring and the dial does not return to a normal rest position. In fact the entire telephone is not what it appears to be at first glance and cannot be used as a ‘normal’ phone, which is why many collectors disregard Inter-Dial telephones.  This does not deter people from offering them for sale on eBay, however!

Inter-Dial telephones were manufactured by Standard Telephones and Cables Ltd (STC), with whom Shipton had a close association for at least five decades. The telephones were made exclusively for Shipton and there is no evidence that STC sold the system. Instead it was sold through electrical wholesalers. Click here for the STC/Bell Antwerp Telephone.


This is a description of the Inter-Dial system, taken from the March 1934 issue of The Practical Electrical Engineer magazine.

An Easily Installed Automatic Telephone System
We had an opportunity recently of examining an intercommunication telephone system suitable for 2 to 11 lines.  This system embodies a basic idea which is sometimes overlooked by manufacturers.  Most British manufacturers today are fully aware of the importance of sound design and good workmanship.  The “Shipton” Inter-Dial telephone system combines with these two points with another very important feature, which is up-to-date appearance.

In appearance and action the Inter-Dial telephone is almost identical with the desk pattern automatic telephone, which has recently been made so familiar to the public by the Post Office Telephone Department.  To call up any station on the Inter-Dial telephone system the dial on the front of the instrument is pulled round in the same manner as when operating a post office automatic telephone.  This selects the required station and the ringing signal is sent by depressing the button in the centre of the; instrument.  To answer a- call it is merely necessary to lift the telephone from the hook.

Thus, for quite a moderate cost, the user of this type of telephone obtains an instrument which is equal in appearance to that which would be used in a fully automatic system the cost of which might run into a thousand pounds or more, whereas a 10-line installation of the interdial system would cost considerably less than one hundred pounds.  In short the system gives a “Rolls Royce” appearance for “Baby Austin” cost.  This feature will commend itself to many users.

A special feature of this telephone is the exceptional speech transmission obtainable from one dry cell. For ringing purposes two additional cells are usually required.  This constitutes the whole of the power; that is to say, three cells only are necessary, fitted in the central position.

The selecting mechanism is of a robust design and consists of materials such as used in the standard Post Office dial, and consequently long life is ensured in the use of these components.

The wiring connections are standard everyday internal telephone practice.  The number and location of the junction boxes depends entirely upon the relative position of the various stations. In wiring up the instrument note that the terminals TC and RC are bridged.

Some electrical contractors may hesitate to install an intercommunication telephone in an office, works, or factory, preferring to leave this to telephone experts.  After examining this particular system we have no hesitation in saying that any electrical man who is familiar with ordinary wiring practice should be able to install and maintain this system.

The pictures and wiring diagrams shown below are taken from the January 1936 catalogue of SUNCO (The Sun Electrical Company of 118-130 Charing Cross Road, London WC2).  The (3x) indication that follows certain prices is not explained but it is suspected that this means that all prices are nett and that in order to qualify for a discount, you need to order three or more units of that particular item.


The wall version of the Inter-dial telephone.  The design is that of the STC (BTMC) ‘Antwerp’ telephone.

Circuit Diagram of the Inter-Dial System

The gold Inter-Dial transfer was in the ‘Hawthorne’ lettering used world-wide by all
companies in the International Standard Electric Company.

Sun Electrical Co. Ltd.

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Last revised: March 14, 2023