C MARKETING INSTALLATION
Issue 1, April 1973
TELEPHONE No. 745 (WEATHERPHONE)
The Telephone No. 745 is a weatherproof telephone for use on
DEL's and PBX extensions in Auto and CB areas on lines up to 1000 ohms. The circuit details are shown in
Click here for the circuit diagram - Web
users - CD users.
COMPONENTS AND CIRCUIT
The transmission circuit is the same as that used on the
Telephone No. 746 but a different printed board is used and two of the components have additional protection against the ingress of moisture. The telephone is protected by neoprene rubber seals between the backplate and body and the body and door. Access to the printed circuit board is gained by opening the door and undoing the two screws, at the top and bottom of the instrument body. When it is required to reassemble the backplate to the instrument body, these screws must be fully withdrawn otherwise they will foul their locating pillars.
A micro switch mounted on the backplate forms the gravity switch. When the handset is correctly clipped into the body, the earpiece depresses a plunger fitted to the body which operates the gravity switch. A screw fitted to the gravity switch mounting bracket provides a lineman's latch. This latch is not self restoring and care should be taken to slacken the screw before reassembling the telephone. After slackening the lineman's latch screw to release the gravity switch the locknut must be tightened to ensure that the screw does not work loose (e.g. due to vibration). Ensure that tightening the locknut does not advance the screw thereby jamming the action of the gravity switch.
The bell mechanism is similar to the
Bell No. 59 except, to provide weather proofing, the armature is fixed to a separate pivot pin which passes through a long bearing fixed through the backplate.
Fitted to the backplate are two twin terminal blocks that are suitable for all sizes of cable up-to 40 lb. conductors.
The dial fitted to the body is a Dial Automatic No. 21 FA Steel. For CB use the dial may be replaced by a Dial Automatic Dummy No. 3A Black.
An additional gravity switch
(Switch No. 20D), used for C wire signalling etc may be fitted, and to provide PBX recall facilities a
Switch No. 27A-1 should be fitted, as shown in Diagram N 845.
Switch No. 26A-1 may be used to provide the bell on-off facility.
The telephone may be fitted to a wall or flat fixture or alternatively may be mounted on a post or pole. For fixing use 3 Screws for Wood No. 12 Csk Hd at least 2in long or 2BA Csk Hd screws depending on the type of fixture.
For pole or post mounting, the following items are available:-
||ITEM CODE No|
|3-6 in||Bracket, Telephone 17A
|6-9 in||Bracket, Telephone 17A
|9-12 in||Bracket, Telephone 17A
The lead-in to the telephone should be enclosed in Conduit No. 2. Secure the conduit to the telephone with locknuts. To prevent the entry of moisture, the end of the conduit remote from the telephone, if external, should be made to point in a downwards direction. This end should also be fitted with a Bushes Conduit Smooth Bore F to prevent abrasion of the cable. If it is considered suitable a cable gland may be fitted to the telephone conduit bush and the conduit omitted.
To fit a
Switch No. 20D alongside the existing gravity-switch:-
(i) Remove the four screws securing the gravity switch bracket to the baseplate.
(ii) Remove the screw securing the micro-switch to the bracket.
(iii) Place the Switch No. 20D alongside the existing gravity switch micro-switch so that the peg in one locates with the hole in the other.
(iv) Locate the two switches between the side limbs of the gravity switch bracket and secure with the screw provided with the Switch No. 20D.
(v) Screw the gravity switch bracket back onto the backplate.
(vi) Route the connection leads to the left of the bell mechanism to prevent fouling the bell armature and terminate in accordance with the circuit diagram.
When it is required to have the door locked, replace the dummy lock by a
Lock No. 43A, transpose the lock plate stored on the right-hand side of the backplate and the two sealing screws fitted to the interior of the body cavity.
To adjust the bell gongs, loosen the two bell clamping screws that protrude through holes in the printed board, rotate the gongs to obtain the required adjustment and retighten the clamping screws.
To obtain this adjustment it is not necessary to dismount the telephone. The gongs can be rotated by applying pressure to the edge of the gongs with a finger and the armature moved smartly from poleface to poleface to ensure that a clear ring is obtained from each gong.
GRAVITY SWITCH ADJUSTMENT
The gravity switch itself should not require adjustment. If incorrect operation of the gravity switch does occur check that the body of the telephone is seating correctly on the backplate before opening the telephone and that the plunger is free in the body. The screws securing the case to the backplate should be fully tightened as this will affect the operation. Due to misuse the receiver hook may be distorted and cause non-operation of the gravity switch. This is usually evident by the fact that the handset will not securely clip into position. This condition can be corrected by removing the hook and bending with a pair of pliers until satisfactory operation of the gravity switch can be obtained.
The following items are available:-
Handset No. 3 Black
Cord Inst No. 4/113AX 6 in (Cord for Handset No. 3)
Switch No. 20D
Switch No. 26A-1
Switch No. 27A-1
When it is required to have the door locked, a
Lock No. 43A (Item code number 434584) is available.
Telephone No. 8745 was fitted with high impedance bell coils and a new style
Plug and Socket cord.
Circuit diagram N845.
Click here for the circuit diagram - Web
users - CD users.
How to wire your Telephone No. 745 to make it work on Plug and Socket
Made by Ericsson - Model N1248A1
|Tele 745||Mk 1||y||5/68|| |
|Tele 745M||Mk 1||y||12/77||Metric conduit entry|
|Tele 745P||Mk 1||y||11/83||Push button version|
| || || || ||PBU 80A - for Loop Dis|
| || || || ||PBU 81A - MF4|