Field Telephone Amplifier No 1

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Field Telephone Amplifier No1

Purpose and facilities

The Amplifier Field Telephone No. 1 is a single stage amplifier designed to extend the working range of army field telephones. The direction of amplification is controlled by a switch and “over-over” working is therefore necessary.
The amplifier, contained in a sealed, waterproof case, is suitable for use in tropical climates and is carried together with its battery in a canvas haversack.
The amplifier is not suitable for use on carrier or repeatered channels.

The amplifier is designed to accept the speech output of a Telephone Set F or L without overloading. If used in conjunction with a high output telephone such as the Telephone Set J, the amplifier would overload.
An attenuator is therefore provided inside the case, which is normally strapped out, but the links are removed when the amplifier is used with the Telephone Set J. 

Range of working

The range of working using an amplifier at each end of the circuit is approximately 27 to 40 miles of D8 twisted cable depending on whether the cable is wet or dry.
The corresponding figures for D3 cable are 19 to 30 miles.

Controls and connections

The receive gain of the amplifier can be regulated by the volume control marked REC. GAIN; this control is only operative when the switch is at REC. The switch must always be restored to this position after conversation is over, otherwise no ringing indication will be received and also the useful life of the battery will be appreciably shortened.
Connection to the telephone is made by means of a twin connector attached to the amplifier panel, while a 5-point connector at the bottom of the case is plugged into the battery.

Power supply

Battery, dry HT/LT 150/3V No. 3 or Battery, dry HT/LT 162/3V No. 2 or No. 1 may be used.

Amplifier Field Telephone No 1.jpg (78956 bytes)

The Manual Contains the Following :-

1 Purpose and facilities
2 Range of working
3 Controls and connections
4 Power supply
5 General construction
6 Weights and dimensions

7 Preliminary
8 Connecting up
9 Operating

10 General
11 H.T. and L.T. check
12 Ringing circuit


1 General view of Amplifier Field Telephone No. 1

2 Plan of panel—Amplifier Field Telephone No. 1

3A Diagram showing position of links when Telephone Set F or L is used

3B Diagram showing position of links when Telephone Set J is used

4 Plan of socket on the battery with position of connector shown in black

5 View of interior of Amplifier Field Telephone No. 1

6 Circuit diagram—Amplifier Field Telephone No. 1

Please Note There are no component values

Amplifier Field Telephone No 1 2.jpg (18473 bytes)

Manual Circuit and
Operation Instructions
available Details Below
As a Download

Click Here

Field Telephone Amplifier No1
Manual containing 10 pages including the Circuit with Component numbers but no values and the layout.

Manuals are Available Worldwide as a Download.

Manual 10 A4 pages worldwide

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We do all we can to provide the very best that is available for you.
But in the unlikely event that any data should not be as you expected.
A refund is always available. Kind Regards Allen and Alanna.

Manuals are Available Worldwide as a Download

Thank you for your interest. Allen and Alanna G0RIT
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Revised: February 09, 2021