SWITCHBOARD
CB 887, AT1810 & AT3718


ENGINEERING INSTRUCTIONS
TELEPHONES
P.B.X.s
B 1080
Issue 1, 5.12.38

PRIVATE MANUAL BRANCH EXCHANGES
Details of Switchboards AT 1810, AT 3718 and CB 887

1. General
This Instruction describes the details of, and the facilities provided by, "Switchboards,  AT 1810, AT 3718 and CB 887," which are floor-type double-cord switchboards designed for use on the systems shown in Table 1.

TABLE 1

Switchboard    System for which designed
AT 1810    Automatic
AT 3718    C.B. (manual) and automatic
CB 887    C.B. (manual)

2. Supersession
These switchboards are now obsolescent and are superseded for new work by "Switchboards, AT 3796" (see B 1030).

3. Equipment, capacity, dimensions, and weights
Table 2 gives the equipment and capacity for the several existing sizes of each switchboard, and Table 3 the dimensions and weight.

4. Wiring
The wiring of the switchboards is complete for the capacity quoted in Table 2, except in the case of the 10 + 60 (180) sizes, in which extension wiring is only provided for 120 circuits. Wood spacing-strips occupy the unequipped indicator and jack positions.

TABLE 2
EQUIPMENT AND CAPACITY OF SWITCHBOARDS, AT 1810, AT 3718 AND CB 887

Type    Size    Exch line
Capacity   
Exch Line Equip    Extn
Capacity   
Extn Equip    Cord cct Capacity    Cord cct Equip
AT 1810    10+30 (60)     10    10    50    30    15    11
AT 3718    10+30 (65)    15    10    50    30    15    11
CB 887    10+30 (65)    15    10    50    30    15    11
AT 1810    10+50 (60)    10    10    50    50    15    15
AT 3718    10+50 (65)    15    10    50    50    15    15
CB 887    10+50 (65)    15    10    50    50    15    15
AT 3718    10+60 (180)    20    10    160    60    18    15
CB 887    10+60 (180)    20    10    160    60    18    15

TABLE 3
DIMENSIONS AND WEIGHTS

Type    Size    Height    Width    Depth overall    Approx. weight (lb.)
AT 1810    10+30 (60)    4' 7"    2' 3.5"    2' 2.5"    280
AT 1810    10+50 (60)    4' 7"    2' 3.5"    2' 2.5"    309
AT 3718    10+30 (65)    4' 7"    2' 1"    2' 2.5"    280
AT 3718    10+50 (65)    4' 7"    2' 1"    2' 2.5"    309
AT 3718    10+60 (180)    5' 1"    2' 2"    2' 6.5"    336
CB 887    10+30 (65)    4' 7.5"    2' 3.5"    2' 2.5"    280
CB 887    10+50 (65)    4' 7    2' 3.5 "    2' 2.5"    309
CB 887    10+60 (180)    5' 1"    2' 6.5 "    2' 4"    336

5. Diagrams
The diagrams relating to the switchboards are in the N series.

6. Transmission data
The maximum permissible resistance for exchange line plus extension is given ,in the following E.I.s:-
TRANSMISSION, Telephone,
B 3503 C.B. manual and automatic areas
B 3504 C.B. manual and automatic areas (divided cord-circuits)
B 3505 L.B. telephone in C.B. manual and automatic areas
B 3550/1 L.B. exchange areas
B 3590 Inter-switchboard extensions.

7. Design and equipment
The design and equipment of these switchboards is similar to that of TELEPHONES P.B.X.s B 1080

(a) "Switchboard, AT3718"
The circuit arrangements do not permit the use of a " Keysender No. 5..." without modification to the board.

(b) " Switchboard, AT 1810."
The exchange holding and through-clearing arrangements, also the dialling keys, are in the terminations of the exchange lines instead of in the cord circuits. The dialling keys, one per exchange line, are fitted in the face of the switchboard above the exchange line indicators.

(c) " Switchboard, CB 887."
As for " Switchboard, AT 1810," but without dialling keys or dial.

8. Power-supply data
All the above switchboards are run on 12 volts DC.

 
 
 
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Last revised: November 27, 2010

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