Every requirement for a weatherproof telephone for roads, railways, building sites, etc, is met in the design of this instrument for wall, or pole mounting. These requirements include compactness, light weight, robustness, durability, high-quality transmission, low cost, low maintenance liability, and security against unauthorised use. Provision for an Operator Recall press button when specified is made in the Automatic and C.B. telephones.

Electrical characteristics equivalent to those of the BPO Type 746 telephone ensure wide frequency response and volume efficiency over lines of up to 1000 ohms loop resistance.

Construction
The use of materials liable to corrosion is avoided. The enclosure, consisting of a base, a body and a hinged door, is of corrosion-resistant aluminium alloy. Other parts are of brass, phosphor-bronze and high-quality stainless steel.

The body is a robust aluminium-alloy casting, webbed to form a solid internal shelf for the handset and drilled as necessary for the dial and/or press button. Two screws inside the body secure it to the base, on which the remaining components are mounted.

The door-another aluminium-alloy casting-has brass hinges and a phosphor-bronze catch. It is channeled to mate with the rim of the body so that foamed Neoprene in the channel excludes moisture when the door is shut. The automatic catch is plunger controlled, a single motion of the hand sufficing to release it and flip open the door. Self-closing doors, and doors equipped with locks are available to special large-quantity order.

The stove-enamelled hard-aluminium-alloy base, with three hollow bosses on its underside for mounting purposes, fits well inside the telephone body and compresses a foamed Neoprene strip to make the joint weatherproof, Two brass bosses threaded for 1/4in diameter conduit are attached to the bottom of the base for the entry of external wires. For magneto working, a cast aluminium-alloy enclosure for the batteries is fixed to the bottom of the base the conduit entries are then in the bottom of this auxiliary enclosure, and the incoming wires connect to a terminal block from whence they are permanently wired through an insulated hole into the telephone base.

Installation and Maintenance
Installation is facilitated by the telephone body being separate from the base, enabling the base to be fixed and the external wires terminated before the body is attached.

For maintenance access to all components and wires is gained on:

(a) removal of two body-fixing screws

(b) closure of the door to protect the handset

(c) withdrawal of the instrument body, suspending it from the fixed base by the nylon cord provided.

Mounting Adapter
A simple form of non-slip adapter is supplied for pole fixing, consisting of a suitably drilled plate with two stainless-steel worm clips. These are available in three sizes and adjustable to suit poles between 3in and 12in (76mm and 305mm) diameter.

Components and Finish
Components similar to those in the conventional BPO Type 706 telephone and therefore of proven reliability are used.

The handset, with temperature-resistant coiled cord, is moulded in high-impact plastic. The handset is held in

position by a stainless steel 'rest' at the receiver end and a phosphor-bronze clip at the bottom.

The dial number-ring has black characters on a white ground. Unless otherwise specified, dials have standard numbering and a 2:1 break/make ratio. The stainless steel 4in (102mm) diameter ringer gongs are mounted on the underside of the base so that signals can be clearly heard.

A transistor ringing-current generator is contained within the magneto version and actuated by simple depression of a switch. A box for four ordinary torch cells is fitted at the lower end of the telephone. Apparatus finishes are suitable for the tropics, and connecting wires are insulated with PVC, which is impervious to moisture and not subject to mould growth or insect attack.

The front of the telephone displays a raised silhouette of a handset in light grey to contrast with the darker background colour. The general interior and exterior hammer finish of the body is light-grey stove enamel.

Dimensions and Weights
617/1/02186 Auto with press button/Auto without press button.
617/1/02187 CB without press button/CB with press button.
Both telephone types:-
Height 12.75in.
Width 5.75in.
Depth 6.75in.

Weight 10.5 lbs.

617/1/02188 Magneto
Height 17.5in.
Width 5.75in.
Depth 6.5in.

Weight 14.75 lbs.

Also available are:-
617/1/02186/000 - Automatic with dial but without press button recall.
617/1/02186/005 - Automatic with dial and press button recall.  Used in Australia.
617/1/02187/014 - CB Used on Motorways.
617/1/02187 - Magneto.

These telephones were sold with or without a Regulator.  If a Regulator is not fitted then Terminals 13, 21 and 27 are linked together.

There may also be a Resistor between Terminals 23 and 24.  This reduces transmission issues on short lines, but can be removed if transmission issues occur.

617/1/02186/000 circuit diagram N109840

Click here for the specification

The bell or ringing device should be 4000 ohms resistance.  This can be rectified by either fitting the correct ringer or by inserting a 3.3K resistor in series with the ringer.

Telephone is wired as follows:-

1. Remove strap between terminals T17 - T18.
2. Insert strap between terminals T13 - T14.
3. Insert strap between terminals T18 - T19.
4. Insert straps between terminals T7 - T8 - T9 - T10.
5. Red wire of line cord to terminal T13.
6. Blue wire of line cord to terminal T18.
7. White wire of line cord to terminal T10.
8. Green wire of line cord to terminal T2.
9. Insert a 3.3K resistor between terminals T19 - T20.
10. Insert a Rectifier No. 205 (if needed) between terminals T24 and T25.

The BT called the new style plug ended line cord a Cord Connecting No 4/502.

There maybe a resistor between Terminals 23 and 24.  This reduces transmission when close to an exchange.  If there are transmission issues then remove the resistor.

617/1/02186/000

Last revised: June 25, 2026