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The G.E.C. loudspeaking telephone is contained in an attractive polished-wood cabinet for standing on a desk or table. It allows the user to carry on a telephone conversation while having both hands free to make notes or consult papers and, as such, is an invaluable supplement to a P.A.X. or P.A.B.X. telephone system. The telephone is intended primarily for use by executives. When it is connected to a private automatic exchange, keys can be fitted to give direct access to up to as many as twenty other extensions. Facilities can also be provided to give the executive priority when a wanted extension is engaged.

The high output volume and sensitive microphone, which are an integral part of this instrument, permit the user complete freedom of movement to leave his desk, e.g., to obtain data or correspondence from a nearby filing cabinet, whilst continuing the telephone conversation.

The high output volume and sensitive microphone, which are an integral part of this instrument, permit the user complete freedom of movement to leave his desk, e.g., to obtain data or correspondence from a nearby filing cabinet, whilst continuing the telephone conversation.

Reproduction is clear and distinct, particularly when reverberation in the room is minimised by sound-absorbing materials, such as carpet and curtains. The high output volume and the feature of two loudspeaking telephones operating together loud-to-loud are derived chiefly from the action of a voice-operated switching arrangement, which automatically accomplishes the function achieved in other instruments by a manually-operated talk/listen switch. Acoustic feedback, the phenomenon often referred to as howling, which imposes severe restriction on the amount of amplification possible in other loudspeaking telephones, cannot occur because when the transmit circuit is open, the receive circuit is automatically closed, and vice versa. Any number of loudspeaking telephones can be employed on a system with direct loud-to-loud speech between them, and each with its own individual group of direct-access extensions.

Rear view of Loudspeaking Telephone with door open to show apparatus


An incoming call is signalled by a buzzer and by the flashing of a red lamp. It is answered by depressing the dial/answer key.

There are two methods by which an outgoing call can be made from a loudspeaking telephone by dialling or by direct-access key calling, when fitted.

Calls from the loudspeaking telephone to any extension on the exchange are made by dialling the appropriate number in the usual way.

Even greater ease of use is given when the loudspeaking telephone is fitted for direct access. With this facility any one of up to twenty selected extensions may be called by operating the appropriate key. Dialling is not necessary.

Should the wanted extension be engaged, a green lamp lights on the front of the loudspeaking telephone. If the direct-access key is left in the operated position, the required extension will be rung as soon as it is free. Alternatively, the caller can use his priority facility as described below, or clear down and recall later. The extensions selected for direct access from the loudspeaking telephone can be altered easily as required.

Should the loudspeaking telephone be engaged on a direct-access call when a call is received from the exchange, the audible signal does not sound, but the calling lamp flashes. The user may take the call, let it wait or, by momentarily depressing the dial/answer key, indicate to a caller that he is busy.

Throughout the system, all conversations are secret and cannot be overheard by other extensions not parties to the call. A handset is provided at the loudspeaking telephone and, when this is used, the loudspeaker is disconnected and incoming speech is not heard by other parties in the room. A microphone cut-off key allows the loudspeaking telephone user to have a local conversation without being overheard by a distant party.

When the user of a loudspeaking telephone finds his wanted party is engaged, he can break in on the established call. This interruption may be controlled by a priority key, or may be made automatic for all calls by inserting a strap between terminals inside the instrument. The extensions already in conversation are warned by a tone signal that a third party is on the line.

The normal volume from the loudspeaker can be increased, when required, by the depression of a key on calls to all extensions, or can be permanently increased on four direct-access lines by inclusion of a strap in the instrument.

Equipment can be supplied to allow a telephone conference to be held between the loudspeaking telephone user and up to ten other extensions. Each of these extension telephones must be fitted with a pushbutton and connected to the exchange unit via the conference equipment. The conference is arranged by each participant being individually called by the convener; at the appointed time, each extension presses the pushbutton on his instrument to give direct connexion to the conference circuit.

Alternatively, a limited conference can take place between the loudspeaking telephone, any one of the direct-access extensions, and any one other extension on the private exchange without fitting any additional equipment.

NOTE: When more than four people are participating in a conference at any one time, it may be necessary for the loudspeaking telephone user to use the handset.

The complete apparatus, including the transistor amplifier, is housed in an attractive desk-mounting cabinet. The microphone and loudspeaker are housed at the front of the cabinet, and the amplifier on the rear door, which can be easily removed when required for servicing, etc.

The sloping front of the cabinet houses the dial, operating keys and supervisory lamps. Alongside the operating keys, space is provided to fit the direct-access keys when required.

The apparatus required to give the direct- access and/or conference facilities is mounted on jack-in plates, which are housed on a wall- mounting shelf. One direct-access connector or one conference circuit is mounted on a single plate and several plates can be mounted on the shelf. This is most conveniently and economically installed near the exchange so that the cable connecting them can be kept as short as possible.


Loudspeaking telephone with key calling and direct access  - TEL/1L/ATU
Loudspeaking telephone without key calling and direct access - TEL/3L/ATJ

Taken from the GEC Catalogue Leaflet No. STL 15

See also GPO LST No. 2

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Last revised: March 13, 2021