Actual circuit wiring diagrams for BPO telephones will be found linked from the relevant telephone page or linked from the N diagram main page. For CD users, the diagrams are held on the CD and will be transferred to your computer on installation.
Go the the BPO telephone list, click on the telephone of your choice - if a diagram is available then a link will be found (contact the author if you need a diagram that is missing).
BPO diagrams and drawings are either numbered or numbered with a lettered prefix. The prefix on diagrams may be one or two letters of the alphabet and those with A, F, K, M, P, Q, S, U, W or X as the third letter of the prefix code take the same number of the associated circuit diagram. The letters have the following significance:-
A - Apparatus or equipment
F - Floor plan
K - Trunking
M - Maintenance
P - Assembly
Q - Stock lists
S - Circuit
U - Shelf jack wiring or U link connections (J or SA series)
W - Wiring or routed circuit wiring
X - Cross-connection
In addition to the above joint circuit and wiring diagrams are given the basic and wiring codes, e.g. RP/RPW
Drawings are numbered in the range 60000 - 99999
Diagrams in general use are:-
General Wiring Diagrams are prefixed with SA
Wiring Diagrams that show wiring runs and wire colours are prefixed with SAW
Police apparatus diagrams are prefixed with PA
Fire alarm wiring diagrams are prefixed with FA
House Exchange systems are prefixed with Q
Testing diagrams are prefixed with T
Telephone wiring diagrams are prefixed with N
Telegraph wiring diagrams are prefixed with TG
List of all Diagram types:-
| Prefix Code | Description | Remarks |
| 1 to 500 399 | Fully dimensioned drawings of apps and equip approved for production | |
| AD | Air Defence drawings and diagrams | |
| ADA | Air Defence drawings and diagrams | |
| ADF | Air Defence drawings and diagrams | |
| ADK | Air Defence drawings and diagrams | |
| ADL | Air Defence drawings and diagrams of cable networks | was ROC |
| ADP | Air Defence diagrams | |
| ADU | Air Defence diagrams | |
| ADW | Air Defence diagrams | |
| ADX | Air Defence diagrams | |
| AGS | UAX No. 7 diagrams | |
| AS | Area of search plans for Repeater stations | |
| AT | Auto exchange ccts; wholly or partially electronic; trunk toll; misc ccts | |
| AT/ATW | Auto exchange ccts; wholly or partially electronic; trunk toll; misc ccts | |
| ATM | Auto exchange ccts; wholly or partially electronic; trunk toll; misc ccts | |
| ATU | Auto exchange ccts; wholly or partially electronic; trunk toll; misc ccts | |
| ATW | Auto exchange ccts; wholly or partially electronic; trunk toll; misc ccts | |
| ATX | Auto exchange ccts; wholly or partially electronic; trunk toll; misc ccts | |
| AU | Auto exchange ccts; wholly or partially electronic; trunk toll; misc ccts | |
| BB | Broadband utilization | |
| BM | Cable and network diagrams | |
| C | Cable and network diagrams that are security classified | |
| CB | CB exchange ccts | |
| CBU | CB exchange ccts | |
| CBW | CB exchange ccts | |
| CBX | CB exchange ccts | |
| CU | CB exchange ccts | |
| CBS | CBS exchange ccts | |
| CBSU | CBS exchange ccts | |
| CBSW | CBS exchange ccts | |
| CBSX | CBS exchange ccts | |
| CBU | CBS exchange ccts | |
| CBW | CBS exchange ccts | |
| CBX | CBS exchange ccts | |
| CC | Communication charts | Regional |
| CCS(L) | Cable cross section diagrams | |
| CD | Contour drawings insufficiently dimensioned for inclusion in main series | |
| CN | External plant and protection | |
| CSU | CBS exchange ccts | |
| CTS | Drawings, diagrams etc for training branch | |
| CU | ||
| CV | Valve charactoristic curves | |
| CX | ||
| D | Boundary maps, key plans and cable network diagrams covering the whole country | |
| DL | Drawing lists for selected jobs | |
| DR | Drilling for apparatus | |
| DT | Data transmission and associated equipment | |
| DTN | Telegraph defence ccts and accommodation plans | |
| DTW | Data transmission and associated equipment | |
| DT/DTW | Data transmission and associated equipment | |
| DWL | Data transmission and associated equipment | |
| E | Diagrams of non-STD transmission equipment and early equipment | |
| EC | Installation particulars of equipment | |
| ECW | Installation particulars of equipment | |
| ED | Drawings of Transmission equipment | |
| EDA | Drawings of Transmission equipment | |
| EG | Drawings and diagrams for electronic exchanges | |
| EGA | Drawings for electronic exchanges | |
| EGC | Diagrams developed under the auspices of the JERC | |
| EGF | Diagrams developed under the auspices of the JERC | |
| EGN | Diagrams developed under the auspices of the JERC | |
| EGU | Diagrams developed under the auspices of the JERC | |
| EGX | Diagrams developed under the auspices of the JERC | |
| EQ | Semi-auto equipment fire emergency ccts | |
| ER | Semi-auto equipment fire emergency ccts | |
| ES | Accommodation and equipment layout plans of buildings | was EX SK series |
| ETC | Drawings, diagrams etc for training branch | was CTS series |
| ETE | Drawings and diagrams of Radio stations, Tele Exchs & Telegraph layouts | |
| EW | Non-standard transmission equipment | |
| E/EW | Non-standard transmission equipment | |
| EX | Drawings and diagrams for all divisions in research branch, except R12 | |
| EX/SK | Superceded by ES series | |
| F | Main cable development forecast diagrams | |
| FA | Fire alarm ccts | |
| FA(L) | Fire alarm ccts | |
| FAW | Fire alarm ccts | |
| FDA | Drawings for factory divisions | |
| FDH | Drawings for factory divisions | |
| FY | Drawings for factory divisions | |
| GMT | Clocks and Greenwich mean time cct | |
| GMTW | Clocks and Greenwich mean time cct | |
| HF | HF diagrams | |
| IF | Factory diagrams | |
| LA | Circuit lab diagrams | |
| LD | Label diagrams for pasting into instruments | |
| LFS | Factory drawings | |
| LL | Drawings of local line network | |
| LR | Misc drawings and diagrams | |
| MISC | ||
| MOH | Drawings of items provided for the department of health | |
| MS | Experimental and temporary ccts | |
| MSU | Experimental and temporary ccts | |
| MSW | Experimental and temporary ccts | |
| MSX | Experimental and temporary ccts | |
| MT | Vehicles and associated equipment | |
| MTF | Methods for fitting items on vehicles for M Branch | |
| MU | Main underground HF and carrier cables, land end and sea earth cables | |
| MU-FM | Main underground HF and carrier cables, land end and sea earth cables | |
| MU-TT | Test tablet diagrams. Suffix TT added to associated MU number | |
| MU4000(HF) | Main network diagrams, motorway cables layout diagrams | |
| MW | Main network diagrams, motorway cables layout diagrams | |
| N | Telephone, Call offices and pbx ccts | loose leaf |
| ND | Network diagrams of private ccts | |
| NT/NTA | Ex National Telephone Company | |
| PA | Police alarm ccts | |
| PA(L) | Police alarm ccts | |
| PF | Phonogram and tele/telegraph ccts and installations | |
| PFU | Phonogram and tele/telegraph ccts and installations | |
| PFW | Phonogram and tele/telegraph ccts and installations | |
| PFX | Phonogram and tele/telegraph ccts and installations | |
| PLAN | Miscellaneous diagrams, maps, networks and proposals | |
| P/DC | Telecoms power plant ccts | |
| P/DCW | Telecoms power plant ccts | |
| P/EL | Electric light fittings | |
| P/ELD | Illumination intensity | |
| P/HG | Heating layouts. Boiler room and fuel hopper arrangments | |
| P/LG | ||
| P/MSC | Miscellaneous | |
| P/P | Engine room, switch gear wiring diagrams | |
| P/PN | Pneumatic diagrams | |
| P/TC | Power plant drawings | |
| P/VN | Ventilation layouts | |
| Q | House exchange telephone systems | loose leaf |
| Q(L) | House exchange telephone systems | loose leaf |
| R | Master copies of tracings from blanks, illustrations for books etc | |
| RA | Relay adjustment cards | |
| RES | Drawings and diagrams for all divisions in research branch | |
| RP | Repeater and amplifier equipment and ccts | |
| RPA | Repeater and amplifier equipment and ccts | |
| RPW | Repeater and amplifier equipment and ccts | |
| RPX | Repeater and amplifier equipment and ccts | |
| ROC | NOW ADL | |
| RSF | Repeater station distribution frame layouts | |
| RSS | Repeater station distribution frame layouts | |
| RT | Automatic exchange routiner ccts | |
| RTM | Automatic exchange routiner ccts | |
| RTU | Automatic exchange routiner ccts | |
| RTW | Automatic exchange routiner ccts | |
| RTX | Automatic exchange routiner ccts | |
| RW | Automatic exchange routiner ccts | |
| S | Parts and composite parts of common use | |
| SA | Circuits of telephone subscribers apparatus | |
| SA(L) | Circuits of telephone subscribers apparatus | |
| SA/SAW | Circuits of telephone subscribers apparatus | |
| SAJ | Circuits of telephone subscribers apparatus | |
| SAW | Circuits of telephone subscribers apparatus | |
| SAX | Circuits of telephone subscribers apparatus | |
| SC | Scales for electrical measuring instruments | Previously on CD |
| SD | Standard data | |
| SHEET | ||
| SUB/A | Woolwich data drawings | |
| SUB/B | Dover data drawings | |
| SUB/C | Dalmuir data drawings | |
| SUB/D | CS Ariel drawings | |
| SUB/E | CS Iris drawings | |
| SUB/F | CS Alert drawings | |
| SUB/G | CS Sentinel drawings | |
| SUB/H | Southampton CMD drawings | |
| SUG/J | Misc Nautical drawings | |
| SUB/K | Foreign charts | |
| SUB/L | Contracts charts | |
| SUB/LS | Misc equipment affecting all ships | |
| SUB/M | Beacons at shore ends | |
| SUB/N | Methil cable depot | |
| SUB/P | CS Monarch drawings for cable ship equipt for PO use use designed externally | |
| SUB/Q | CS Monarch drawings for cable ship equipt for PO use use designed externally | |
| SUB/R | Cable section sheets | |
| SUB/S | PO designed equipment | |
| SUB/T | Cable shore ends | |
| SUB/U | Common equipment for new ships | |
| SUB/V | ||
| SUB/W | CS Iris | |
| SUB/X | Greek consultancy | |
| SUB/Z | Sketches, schedules, graphs etc | |
| SUP/D | Packaging | |
| T | Testing circuits and diagrams | |
| TG | Telegraph ccts | |
| TG(L) | Telegraph ccts | loose leaf |
| TGM | Telegraph ccts | |
| TGK | Telegraph ccts | |
| TGU | Telegraph ccts | |
| TGW | Telegraph ccts | |
| TGX | Telegraph ccts | |
| TK | Auto exchange trunking and grading diagrams | |
| TL | Telephone, trunk, misc and power | |
| TLU | Telephone, trunk, misc and power | |
| TLW | Telephone, trunk, misc and power | |
| TLX | Telephone, trunk, misc and power | |
| TP | Telephone exchange equipment installation drawings and diagrams | |
| TPW | Telephone exchange equipment installation drawings and diagrams | |
| TPX | Cross connection field for meter pulse supplies | |
| TRT | Testers for telephone exchange equipment | |
| TRTM | Testers for telephone exchange equipment | |
| TSB | Diagrams for test equipment | |
| TSL | Diagrams for test equipment (test section Studd Street) | |
| TSU | Drawings and diagrams for the Technical support unit | |
| TTC | Training branch material | |
| TU | ||
| WB | Laboratory drawings and diagrams | |
| WB/WBM | Laboratory drawings and diagrams | |
| WBM | Laboratory drawings and diagrams (assembly) | |
| WBW | Laboratory drawings and diagrams | |
| WE | War emergency diagrams (1939) | |
| WL | Radio station drawings and maps | |
| WM | Radio station drawings and maps | |
| XED | Drawings and diagrams of non-standard equipment for experimental purposes | |
| XM | ATE crossbar exchanges 5005 | |
| XP | ATE crossbar exchanges 5005 | |
| XQ | ATE crossbar exchanges 5005 | |
| XS | ATE crossbar exchanges 5005 | |
| XX | ATE crossbar exchanges 5005 | |
| Y | Diagrams and drawings for R12 | |
| Z | Drawings and diagrams for RS division before transfer to GCHQ | |
This list is included in the Diagram spreadsheet
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