WORK IN THE LONDON CONTROL ROOM A contemporary account of this area from the 1934 BBC Year Book. Earlier issues had included descriptions of the equipment found in the studios and the Control Room...

...The story, however, would not be complete without a few words being said of the work which falls to the lot of the Control Room Engineers not only in maintaining all the plant but in adding that human element which is so vital to the smooth running of broadcasting.

In the London Control Room, since there is activity throughout every hour of the twenty-four, engineers are always on duty. They work in three sections - two large sections for the day and evening, and a smaller section for night work, engineers being allotted to the different sections each week according to a rota. The day section starts at 9 a.m. As the actual work that each engineer carries out is in most cases dependent on the subject-matter of the programmes to be broadcast or of the rehearsals or special tests taking place, it is best first of all to see what this entails.

Throughout the "office" day there is a stream of memoranda pouring in from all the various departments of Broadcasting House, such as "Music," "Outside Broadcasts," "Productions" and many others who have an active interest in the work which is required of the Control Room. This flow is centred on a very small but vital section of the control room staff. As an example, there may be a very urgent request for a special microphone lay-out for a "stunt" item to be broadcast in an hour's time - this must be dealt with immediately. Equally there may be detailed instructions for a discussion between speakers in London and New York to be broadcast two months hence, and this requires filing under the date in question. And so it goes on - instructions for the studios to be used for each item of the day's transmissions and for all the numerous rehearsals, with special mention of particular requirements, instructions for recordings to be made by the Blattnerphone, and their subsequent reproduction to the Empire or in the "Home" programmes, details of outside broadcasts, of simultaneous broadcast arrangements, of productions to be controlled on the dramatic control panels, of engineering tests and of a hundred and one other things large and small which ultimately have their direct effect on the programmes as broadcast. Each evening the next day's "operation instructions" must be carefully prepared so that as soon as the first section of engineers comes on duty in the morning each man may know exactly what is required of him for the day. A slip here might easily mean a serious defect in a transmission. For example, a typing error of a D for a C in the special programmes made out solely for the engineers' use might easily cause the control engineer to become highly perturbed at receiving no response from Studio 3D; the speaker concerned meanwhile waiting calmly in Studio 3C for the red light to flick as an indication for him to begin his talk. Dead accuracy here, therefore, is an absolute essential, for once an operating engineer makes a mistake its effect is almost certain to become immediately obvious to the listening public.

Returning to 9 a.m. The fully charged batteries to be used for the day in supplying power to the amplifiers and the signalling and telephone systems have already been connected to the control room bus-bars by the battery engineer, and the discharged batteries, used the previous day, are being recharged by the motor generator sets two floors below the Control Room. The engineers who will be responsible for controlling the programmes are busy calibrating the programme meters on all control positions preparatory to the "line up" test with the Brookmans Park transmitters and the provincial stations. This latter test ensures that all amplifiers in the broadcast chain are adjusted to their correct gain, so that presently the control engineer in London will know that every transmitter taking the programme which he is controlling will be receiving the same input intensity. Similar tests are carried out from the provincial stations to London. Throughout the day all programme meters will be checked from time to time as a safeguard against any discrepancy which may develop...

The work entailed in controlling the programmes and setting up the required programme channels was described in the 1932 Year Book, as follows...

Each broadcast programme has to be continuously controlled by an engineer seated at one of the Control Positions. He has before him a controlling handle, with which he can regulate the volume of the transmission, one or more handles with which he can fade from one programme source to another, a row of keys controlling the signal lamps in all the studios in the building, and a set of special keys by which he is able to set up the particular circuits that he wishes to use.

The engineer has a schedule of the day's programme before him, and his first duty is to set up the circuits for the first two or three studios that will be in use for this programme, by means of the keys on his position. The operation of these keys will switch on the amplifiers required, energise the microphones in the appropriate studios, and bring the outputs of the amplifiers associated with these studios to the fade unit on this Control Position. All this is effected by means of relay switching, the relays being located on the apparatus racks. These relays also cause "engaged" lamps to light on all the Control Positions in both Control Rooms so that the engineer at this position knows that his circuits are set up correctly, and the engineers at other positions know that these particular studios are engaged.

When the programme is due to begin, the announcer in the studio presses a button which operates a buzzer in the Control Room and lights a green light on all Control Positions. The engineer on the particular Control Position which is controlling this transmission depresses a key which puts out these green lights, then throws the key in the opposite direction, which lights a red light in this studio, and also lights a red light associated with this studio on every Control Position. The red lights in the studio give the announcer the signal that all is ready and the programme begins. The engineers seated at other Control Positions take no notice of these lights, since they are not concerned with those particular studios at this time, and on seeing the red lights they know which studios are actually in use for a transmission.

The engineer at the Control Position keeps a continuous check on the programme by means of headphones and maintains the volume within the specified limits, the volume being recorded on a "Programme Meter" on the position. When it is necessary to change from one studio to another or from a studio to an Outside Broadcast, the engineer will set up the second circuit in advance and at the appropriate time will fade from one to the other by means of the fade-unit on his position.

Returning to the article in the 1934 Year Book...

...So we may leave the control engineer who, with his assistant, will be controlling one of the transmissions for most of the day. His assistant, incidentally, keeps a log showing, correct to the second, the time and details of all changes in programme sources, and of all technical faults as heard by wireless, even to a momentary "scratch." This log is of paramount importance to the programme staff in compiling their statistics, in addition to its primary engineering value.

The S.B. (simultaneous broadcast) engineer starts his turn of duty by checking up all programme and technical arrangernents with the nearest provincial S.B. centres, for he will be responsible for ensuring that they receive the correct programme at the correct time, and for most of the day he will be dealing with at least three separate transmissions. He also sees that the Greenwich Time Signal is broadcast according to schedule.

In the meantime the lines termination engineers have been setting up and carrying out insulation, listening and other tests on the circuits to be used for the outside broadcast (O.B.) transmissions and rehearsals to be carried out during the day. Each line requires a certain setting for the amplifier to be used in conjunction with it for "equalising" - that is, for correcting the line characteristics for frequency response. These values have been predetermined after tests carried out by the "Lines Department" engineers. When all is in order the "music" circuit is plugged over to the control position which will require the O.B, whilst the "control" or speaking circuit is plugged up to the supervisory position concerned. The lines termination engineers also deal with all tests and defects on trunk lines. They are the Control Room's linkage with the G.P.O. whether it be Welbeck Exchange for London O.B.s, Trunks for S.B.s, long distance O.B.s and Continental work or Radio Terminal for transmission with New York, Australia, ships at sea and in fact any Post Office radio link.

Another section of engineers is responsible for testing the microphones in the studios. About half an hour before the commencement of every transmission or rehearsal the microphones are listened to through the normal chain of amplifiers, polarising feeds are checked and a very rigid routine is carried out to ensure that even with abnormal usage no technical fault is apparent. It must be remembered that the microphone - being the first link in the chain, and requiring as it does a considerable amount of amplification to bring its signal strength to within control limits - must of necessity be absolutely free from the most minute defects if good transmission is to be obtained. The reason that microphone tests are carried out about half an hour before the microphones come into use is to ensure that they are in good order up to the latest time which is practicable, while also allowing a short time to remedy any defects which may be found. Were microphone circuits to be tested some hours in advance there would always be the possibility of a defect developing after the test.

It falls to the lot of these engineers also to prepare the circuits for all rehearsals which may be required. On an average there are about eight separate rehearsals being carried out at the same time between the hours of 10 a.m. and 6 p.m. (excluding the 1 p.m. to 2 p.m. period) and during a normal day as many as 30 to 40 individual rehearsals are dealt with, each requiring the microphones and associated equipment energised exactly as if it were a transmission. This entails setting up the correct amplifier circuits so that the rehearsal may be listened to on loudspeakers wherever required, and in certain cases the "talk-back" facilities need setting up to suit the particular conditions of studio, listening point, etc., whereby the person listening to the rehearsal may speak over a microphone circuit and by means of a loudspeaker give instructions to those rehearsing in the studio.

Rather similar to the work described above, but very much more complicated, is the preparation of the circuits for dramatic productions using many studios. As will have been gathered from the article on "The Dramatic Control Panels" on p.385 of the 1933 Year-Book, the possible combinations of circuits are endless. The normal lay-out requires usually some three studios, together with echo on perhaps two of them, an effects and a gramophone studio - in all some seven sources of "programme." All these have to be plugged up to the correct positions on the panel as indicated by the producer. Cue light circuits, loudspeakers in listening rooms, headphone circuits, talk-back circuits to loudspeakers in the studios in the case of rehearsals, and probably circuits for recording purposes have to be set up and thoroughly tested before the producer can start his rehearsal. Such an intricate linkage requires the most careful and systematic testing, for it is obvious that when many studio circuits are mixed together a mistake in the setting up would wreck the whole performance, whether it be a rehearsal or a transmission, since it would be extremely difficult, if not impossible, to locate the error once the performance had started.

In addition to those already mentioned, there are the engineers sitting at the supervisory positions dealing with the internal telephonic inter-communication and the engineers checking the transmission quality by loudspeaker three floors below, and the senior control room engineer who is the mainspring of the whole section of engineers.

But this is not the whole of the picture. Side by side with what might be called the main engineering routine there is the work at the Blattnerphone recording apparatus (now largely used for Empire Broadcasting as well as for rehearsal purposes), that connected with gramophone recording, running the television transmissions, and the ultra short-wave transmitter, not to mention the labour of maintaining and cleaning this vast amount of apparatus and wiring, the storage and issue of spare parts, and the testing of the valves actually in circuit (it takes one man a month to do them all).

Finally, there are the engineers responsible for broadcasting the programmes to the Empire throughout the night, and who in their spare time carry out most rigid tests on the loudspeakers which are used in the various listening rooms and studios, in order to maintain a high standard of quality of reproduction.

Add to all this the work entailed in testing out new types of microphones, control room amplifiers, valves, etc., and it will be admitted that the London Control Room and its staff must needs be a large and complex organisation.

In addition to the material on this and the previous page, there is more information about the Control Room in the technical section.

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