The radio equipment listed in this catalog was made by DeForest Radio Telephone and Telegraph Company of New York City.
 
Catalog No. 15, Radio and Electrical Supplies, The William B. Duck Co., 1921, page 35:

WIRELESS  TIME  SERVICE

      All the progressive jewelers are taking advantage of the time being sent out daily by a great number of Government Naval Radio Stations. No knowledge of wireless is necessary to pick up the time. The time is transmitted in the same manner as along the telegraph lines; that is by a series of dots. On the Atlantic Coast the time signals are sent out by the naval stations at Arlington, Key West and New Orleans. The signals from Arlington and Key West are sent out every day in the year twice a day, from 11:55 until noon and from 9:55 to 10:00 P. M., 75th meridian time. The time signals from New Orleans are sent out daily including Sundays and holidays, commencing at 11:55 A. M. On the Pacific Coast the time is sent out through the naval radio station at Mare Island, Eureka, San Diego, Pt. Arguello and North Head, Washington. Signals from Mare Island are sent out every day at 11:55 A. M. and 9:55 P. M., 120th meridian time. From all other stations the signals are sent out daily, excepting Sundays and holidays, at 11:55 A. M., 120th meridian time.

      To hear the signals with greatest distinctness the receiving circuit should be in tune with the sending station. Arlington and Mare Island use a 2500 meter wave length; North Head and San Diego use a 2000 meter wave length, Eureka a 1400 meter wave length, Key West and New Orleans a 1000 meter wave length, and Port Arguello a 750 meter wave length. At the Arlington station the signals or seconds are beat off for 29 seconds with a pause of one second, at the division of the minute into halves. At 9:55½ P. M. the beating of seconds is repeated for 25 seconds when a pause of 5 seconds takes place. Then the signals are repeated in the same manner for five minutes with the exception that the last half of the last minute only 20 seconds are beat off, then a pause of 10 seconds elapses when one long dash is made indicating 12 noon or 10 P. M., which is followed by the signals N A A Va. At 10:00 P. M. the metrological information is sent out following these time signals. Also obstruction notices from hydrographic office are sent out following time signals. We presume that the same method is used with the other stations, but at this writing we have no positive information.

      No license from the government is necessary to install and operate a receiving set, and the cost of installing one is relatively small.

      In addition to the receiving set, it is necessary to have the material for the antenna. Elsewhere in our catalog we give complete instructions for erecting an aerial and a complete list of antenna material. It is a very simple matter to build one if the instructions are followed. We recommend the use of a ground switch and antenna switch with all receiving and transmitting sets. The ground switch will serve to protect the instruments from danger in case of a lightning storm and will also serve as a protection to the building itself from lightning. Any type of ground switch listed on preceding page will be satisfactory for a receiving set The lead-in wire should be securely soldered to the center terminal and the ground and aerial wires to the other two terminals. A wire must also be run from the ground terminal to the ground terminals of the antenna switch, so that when the receiving set is in use, there will be an aerial and ground connection. It will, therefore, be observed that there will be two ground wires running to the ground terminal of the ground switch; one direct to the ground connection and the other to the ground terminal of the antenna switch. For jewelers we recommend that a local wireless amateur be employed to install the receiving set and antenna. There are numbers of them in every town and city.

      The following list of Naval stations is here given for the information of our patrons:
 
 Call
Letters		  Name of Station     Call
Letters		  Name of Station
 
NABPortland, Me. NAQJupiter, Fla.
NACPortsmouth, N. H. NARKey West, Fla.
NADBoston, Mass. NASPensacola, Fla.
NAECape Cod, Mass. NATNew Orleans, La.
NLANantucket Shoals Light Ship. NAUSan Juan, P. R.
NAFNewport, R. I. NAWGuantanamo, Cuba.
NAGFire Island, N. Y. NAXColon. Isthmian Canal Zone.
NAHNew York, N. Y. NAYPorto Bello, Panama.
Pages 92-93:

TYPE  RS-100  JEWELERS  TIME  RECEIVER
 
RS-100       A complete receiving set designed especially for jewelers and watchmakers, with three things in mind: efficiency, cost and simplicity in operation. The last feature should be a particularly valuable one for the jeweler who it is realized is not a radio man, and has no time to make adjustments and experiments in order to obtain results. The set, therefore, is provided with but one control, which when set to a. given aerial need not to be changed, and signals from Arlington, Va., or any other time station should be received consistently day after day without further adjustment.
      The set consists of a bakelite panel on which is mounted one of our type R-100 tube receptacles, type CV-500 variable 90° air condenser, one F-200 filament rheostat, G-100 grid leak, ULC-200 single cell mounting, a Honeycomb Coil of the proper size and binding posts for connection to the aerial and ground, storage battery for lighting the filament, telephone receivers, or a type P-200 two-step Amplifier and loud speaking horn. A 40 volt "B" battery consisting of two of our standard 20 volt units with their remarkably long life is included, so that when once set up, the receiver should require no attention for at least six months.
      The whole outfit is enclosed in an oak cabinet with our handsome "Early English finish." Its small size of 9" X 91/8" X 73/4" takes up a minimum of counter space.
      As the set is equipped with the audion type of detector, it is of the utmost sensitiveness and no difficulty should be experienced in receiving time signals from Arlington on a fair sized aerial when 1,000 miles away. An aerial consisting of a single wire 40 to 60 feet high and 150 to 200 feet in length depending upon the location of the set should be sufficient for such reception.
      We believe the jeweler should welcome this set warmly, due principally to its simplicity which assures him of constant reception of the time signals after he has given up the expensive time service lease, upon which he is at present dependent for the setting of his clocks. The de Forest Jeweler's Receiving Set has the added advantage over the old style time leases, that absolutely the actual time may be obtained with it, whereas telegraph time signals are apt to be inaccurate, owing to mechanical lag in the apparatus, and personal errors in the setting of the master clocks.
      The metal parts of the type RS-100 Receiver are of brass with a nickel polish. Against the black bakelite background, a decidedly pleasing appearance is provided which is worthy of a place on the counter of the most up-to-date and enterprising jewelry store. When the set is used in this way, from an advertising point of view, it is decidedly worth while. A greater and far better advertisement is obtained, however when our type P-200 two-step amplifier and loud speaking horn receiver is added to the set, so that time signals as well as signals from radio telegraph and telephone stations may be heard all over the store. An object of such general interest, it has been found, causes much favorable comment on the part of the public with the result that sales are increased and the store gains a reputation of being the most enterprising and up-to-date.
No. RS-100 Jewelers' Time Receiver Without Tube and "A" Battery, but With "B" Battery and Coil . . . . $30.00
Shipping Weight, 15 lbs.
    Note: Our Type P-200 Amplifiers and Loud Speaking Receivers are described elsewhere in our catalog.
Pages 88-89:

TYPE  P-200  TWO-STEP  AMPLIFIER
P-200
      This is the very latest in amplifier design and will be found to be very different and so much more efficient than our older types of amplifiers that there is no comparison. The most notable feature of the new design is its compactness. The small case contains not only the amplifying coils, telephone jacks, amplifier tube receptacles, and filament resistances, but also a "B" battery of 40 volts which is sufficient to give amplifications up to 10,000 times. All these pieces of apparatus are mounted on the panel and come out with it. The panel is easily removable making all parts most accessible and the replacing of the "B" batteries but a moment's work.
      Unit batteries of 20 volts each, cast in one block, are used. Those come provided with two leads which are connected to the circuit by means of two connecting clips. It is therefore unnecessary to use a soldering iron to connect together a number of cells. Moreover, the new type of battery is the most efficient and practical battery made. It has a remarkable shelf life and operating life of approximately 2000 hours when used with our type VT 21 tubes in this type of amplifier. Users of amplifiers in the past will appreciate this new development in "B" batteries which has taken place during the war.
      The panel is of 3/8" bakelite beautifully engraved. The tube receptacles are nickel plated with a high polish and the knobs and binding posts are of bakelite. These are large in size and are of an expensive and artistic type. The binding posts are provided with slots to hold the wire in place while the head is being screwed down.
      The cabinet is of oak with "Early English" Finish. It is strongly built and beautifully polished.
      In order to operate the instrument it is only necessary to connect a six volt storage battery to the two binding posts marked "A  BATTERY". The source of audio frequency should be connected to the two posts marked "INPUT." If the plug on the telephone cord is then inserted in the jack marked "I  TEL", the audio frequency to which the device is connected will be received unamplified. If then the plug is inserted in the jack "II  TEL" and the filament rheostat marked "FILAMENT  TUBE  I" is adjusted, the audio frequency will be amplified by means of the first step. If a similar operation performed with the rheostat for the second tube after the telephone plug is inserted in the jack marked "III  TEL", the full amplifying power of the instrument will be obtained.
Measurements: 12½" X 93/8" X 73/4"
No. P-200 Two-Step Amplifier without amplifying tubes and "A" battery . . . . $70.50
      Amplifying Tube, with four prong standardized Bayonet Base, each . . . . 7.00
Shipping weight, 35 lbs.
      Licensed under Fleming and DeForest patents.
Page 85:
LS-100
TYPE  LS-100  LOUD  SPEAKING  RECEIVER

    In the up-to-date radio station where amplifiers are employed, the Loud Speaker is fast becoming a necessity, and the use of head receivers is rapidly going out of style, except for the very weakest signals.
    We present a loud speaker which, when used in connection with a two-step amplifier, will cause the signals to be heard all over the operating room. Experiments have shown that a loud signal on these receivers can be amplified to such an extent as to be unbearable to the ears when the head is placed within two or three feet of the horn.
    For the reception of time signals from Arlington, a loud speaking receiver and two-step amplifier is an addition to the receiving set which is especially more than worth while to those who wish to allow several people to set their watches at the same time. Such an equipment has an exceptional commercial value to the jeweler since the time signals may be heard all over his store, and should produce an excellent advertisement for his business.
    The Loud Speaker consists of a special telephone receiver capable of handling fairly large amounts of received current and of an impedance high enough to be inserted directly in the plate circuit of the amplifier or detector. The receiver is equipped with a special shell bearing a threaded portion to which the horn in attached.

No. LS-100 Loud Speaking Receiver, with 20" or 24" bell or cone-shaped horn, as illustrated, six feet cord and plug ceiling or wall type.
$35.00
Shipping Weight 20 lbs.