Radio broadcast .. (1922-30)

392 RADIO BROADCAST FEBRUARY, 1927 the pad at the station end. Gain controls, in the diagram, Fig. i, are represented by diagonal arrows indicating variable am- plification of those stages through which they are drawn. The normal course of a change-over may now be outlined. We start with a per- formance in the studio. The microphone M s is feeding the amplifier designed for its output. The studio announcer finishes his program with a prearranged cue sentence, and shuts off his microphone. During or at the end of this sentence, the control operator, who hears everything radiated by means of a monitoring receiver or other facilities, says to the remote control operator, "You're on the air." He does this by means of a telephone set which may be connected, by means of the double-pole double-throw switch, on the blades of which the line terminates, to that line. The field man, talking into the microphone M f , answers, "Right!" Then, and not until then, the control operator flips the D. P. D. T. switch to the "Air" side, connecting the line to its amplifier. The remote control technician, after his "Right!" has turned the microphone M f over to his announcer, or has made the announcement himself, if he combines the two functions, as is not unusual in small stations. What is spoken to M f now goes out on the air, while M s is dead. The change-over has been accomplished. At the same time, the telephone set, it should be noted, is disconnected, so that if some- one talks to it accidentally, the speech will not go out on the air. The connections and procedure outlined above are of a primitive type compared to the methods actually used in most up-to-date stations. With thirty or forty pairs of wires coming into the control room, the D. P. D. T. switch becomes a regulation telephone switchboard, with keys, jacks, plugs; ringing, talking, and monitoring facilities are there in abundance. The board should prefer- ably be built with two positions, so that one side may be used independently for testing with one out- side point while another is on the air, with less of the ever-present danger of creating a mix-up on the air. The sin- gle microphone, M f , provided at the field point, is usually only one of a number, since otherwise there will be a delay while it is transferred from the operator, who must use it to get on the air, to the concert position. The princi- ple of the operation of changing over remains the same, however. The process of switching back to the studio is simpler than the reverse oper- ation. It is merely necessary for the studio announcer to be given listening facilities, say in the form of a high-im- pedance headphone paralleling the loud speaker in the control room. When the field announcer finishes up with the cue sentence, the studio announcer switches on his microphone and begins to talk; the control operator, at the same time, disconnects the field point from the air, exchanging a few words of summing-up conversation with the field men before they take down their apparatus and leave for the next job. It is considered a mark of finesse in broadcasting to make the change-overs "snappy," leaving scarcely a pause be- tween one event and the next. This idea is carried to an extreme in what is known as the "split-sentence change-over," in which one announcer finishes a sentence begun by the preceding announcer. In going back to the studio from the field, the procedure is, on the technical end, the same as outlined above. The sentence must be agreed upon beforehand. For example, it is understood that the field announcer will say, "We shall now return to our studio, where . . . ." And there he stops. The studio man, with his micro- phone already cut-in, remains silent till he hears "where," then, without a pause, finishes the sentence: "The Ritz trio will entertain you for a half hour." The first time one hears this stunt one gets a hand- some kick out of it. As far as I know, the credit for introducing it around New York goes to WHN although several other stations have used it since. It is somewhat more complicated in the other direction (from studio to field). In this case it is necessary to provide listening facilities for the field announcer. This is done readily on a telephone switchboard by sending the monitoring signal to the Ms FIG. field point over the line for some minutes before the end of the studio program, and letting the field announcer listen on a pair of headphones across the line, in parallel with those of the field operator. This monitoring signal may be secured by taking a tap across the loud speaker in the control room, which, however, it is essential to keep going with adequate volume. When the studio announcer comes to the cue word of the split sentence, the control operator flips a key which disconnects the monitor- ing signal from the line and connects the line to the air. This requires accurate timing, and a slip on the part of the control operator messes up the change-over. He needs to be sober, to be sure. An ex- perienced man, however, will have sur- prisingly few failures, and a well-conducted station can be run for weeks without making an error on split sentence change- overs. One other detail must be looked out for, particularly if one essays split-sentence virtuosity—accurate control of field and studio levels, so that the volume of the two announcers is substantially the same. This equality may be attained by providing listening facilities in the outputs of the first-stage amplifiers, A s and A L , with means, also, for disconnecting either from the succeeding stages of amplification. With one of the two on the air, the control operator listens in its output, then lets the announcer who is to take the air next say a few words, while a suitable level is set by adjustment of the amplification of the first control stage, or the artificial line (if this is variable) or the output of the remote control amplifier. The control operator listens for this in the output of the first stage, not on the air. When the latter is put on the air, some adjustment may be necessary during the first word or two, but if the preliminary setting has been carefully made the inaccuracy will be slight and hardly noticeable. Split sent ence change-overs, while striking and worth trying, have some- thing exhibitionistic about them which makes them unsuit- able for dignified or highly artistic events. They are excellent for ordinary and jazzy programs, but one does not introduce a Philharmonic concert with them. Infact.the speed of the switch- over should be some- what reduced in such a case, not only to lower the risk of a mix-up but because a few sec- onds ofsilenceaddim- pressivenesstothe en- trance of a queen, a president, or a $50,000 radio program. . Grids *• of Modulators