Cased Coil
 |
 Bryant CC5AXA060024 cased evaporater coil $49.00 Time Remaining: 1d 22h 4m Buy It Now for only: $199.00 |
 R410A FULL CASED EVAPORATOR COILS MULTI POSITION 4 TON RIGHT HAND DRAIN $419.99 Time Remaining: 21d 14h 26m Buy It Now for only: $419.99 |
 VERTICAL CASED UPFLOW DOWNFLOW EVAPORATOR COILS 25 TON 21 W X 22 H x 21 D $269.99 Time Remaining: 29d 11h 7m Buy It Now for only: $269.99 |
 R22 FULL CASED MULTI POSITION EVAPORATOR COILS 25 TON W TXV VALVE $299.99 Time Remaining: 21d 14h 54m Buy It Now for only: $299.99 |
 25 TON 17 X 22 VERTICAL CASED EVAPORATOR INDOOR UPFLOW DOWNFLOW COILS $264.98 Time Remaining: 26d 20h 29m Buy It Now for only: $264.98 |
 Bryant 519BXX048000ABAA cased evaporater coil $29.99 Time Remaining: 1d 22h 46m Buy It Now for only: $129.00 |
 3 TON UPFLOW DOWNFLOW VERTICAL CASED EVAPORATOR COILS CAPF3636B6 hvac $289.99 Time Remaining: 2d 19h 53m Buy It Now for only: $289.99 |
 2 TON FULL CASED MULTI POSITION R22 EVAPORATOR COILS w LEFT HAND DRAIN $259.99 Time Remaining: 8d 12h 27m Buy It Now for only: $259.99 |
 Hill 5306 Coil Cleaner Conditioner NEW Case or Can HVAC Multi action cleaner $6.95 Time Remaining: 27d 19h 9m Buy It Now for only: $6.95 |
 15 TO 2 TON VERTICAL CASED SPLIT SYSTEM AC HEAT PUMP EVAPORATOR COILS 17 X 18 $219.99 Time Remaining: 3d 14h 42m Buy It Now for only: $219.99 |
 Goodman 3 Ton Cased A Coill NIB 175 Evaporator Coil $71.00 (9 Bids) Time Remaining: 3d 11h 43m |
 Carrier Evaporator Coils Cased Never Used $89.99 Time Remaining: 17d 7h 54m Buy It Now for only: $89.99 |
 15 TO 2 TON VERTICAL CASED UPLFLOW DOWNFLOW INDOOR AC EVAPORATOR COILS 14 X 18 $209.99 Time Remaining: 24d 13h 37m Buy It Now for only: $209.99 |
 4 Ton Cased Upflow Evaporator Heat Pump Coil Johnson Controls Luxaire York $199.95 Time Remaining: 28d 12h 35m Buy It Now for only: $199.95 |
 CASED COILS R22 AND 410A FROM 2 TON TO 5 TON ALL NAME BRAND LK $100.00 Time Remaining: 28d 20h 5m Buy It Now for only: $100.00 |
 ASPEN HEATING COOLING CASED COIL EXCELLENT CONDITION CLEAN UNIT BVR 2436 AF $150.00 Time Remaining: 3d 17h 3m |
 TRANE 2TXCB025AS3HCAA 2 TON AC HP ALUMINUM CASED A COIL R 22 150728 $202.00 Time Remaining: 7d 11h 48m Buy It Now for only: $202.00 |
 20 TON CENTRAL AIR AC FULL CASE EVAPORATED COILS UPFLOW DOWNFLOW HORIZONTAL $239.99 Time Remaining: 14d 14h Buy It Now for only: $239.99 |
 DAYTON CASED EVAP COIL UPFLOW 2 TON $225.99 Time Remaining: 8d 14h 8m Buy It Now for only: $225.99 |
 ASPEN CE30D44145L015 25 TON MULTI POSITION AC HP CASED A COIL R 410A 163210 $175.00 Time Remaining: 5d 7h 38m |
 R22 25 TON 17 CASED EVAPORATOR COILS MULTI POSITION 17 1 2 W x 20 1 2D $299.99 Time Remaining: 14d 12h 39m Buy It Now for only: $299.99 |
 R410A FULL CASED EVAPORATOR COILS MULTI HORIZONTAL POSITION 2 TON RH DRAIN $239.99 Time Remaining: 1d 13h 8m Buy It Now for only: $239.99 |
 GOODMAN EVAPORATOR COILS CASED CENTRAL AIR CONDITIONER $269.99 Time Remaining: 9d 12h 12m Buy It Now for only: $269.99 |
 R410A 5 TON FULL CASED EVAPORATOR COILS MULTI POSITION RIGHT HAND DRAIN $449.99 Time Remaining: 16d 12h 51m Buy It Now for only: $449.99 |
 2 1 2 TON CASED EVAPORATOR COIL R22 OR R410A $150.00 Time Remaining: 6d 11h 14m Buy It Now for only: $165.00 |
 30 TON CENTRAL AIR AC FULL CASE EVAPORATED COILS R22 $309.99 Time Remaining: 14d 20h 13m Buy It Now for only: $309.99 |
 2 TON R22 CASED EVAPORATOR COILS MULTI POSITION 17 1 2 W x 20 1 2D x 22 1 2H $259.99 Time Remaining: 23d 14h 45m Buy It Now for only: $259.99 |
 R410A 35 TON CASED EVAPORATOR COILS MULTI POSITION 21W x 20 1 2D RIGHT DRAIN $409.99 Time Remaining: 16d 14h 22m Buy It Now for only: $409.99 |
 Haier Coil 35 Ton Multi Positional Cased 205 $419.00 Time Remaining: 16d 22h 36m Buy It Now for only: $419.00 |
 Carrier 25 Ton Cased Slab Coil CSRHP3012ATA R 22 $169.99 Time Remaining: 7d 15h 26m |
 Hvac Direct Coil 25 Ton Up Down Cased 17 $319.00 Time Remaining: 6d 19h 16m Buy It Now for only: $319.00 |
 CENTRAL AC AIR CONDITIONER CASED EVAPORATED COILS 4 TON R22 MULTI POSITION $429.99 Time Remaining: 9d 13h Buy It Now for only: $429.99 |
 Hvac Direct Coil 25 Ton Up Down Cased 14 $304.00 Time Remaining: 20d 3h 31m Buy It Now for only: $304.00 |
 Carrier 35 Ton Cased Slab Coil CSRHP4212ATA R 22 $199.99 Time Remaining: 7d 15h 26m |
 Haier Coil 4 Ton Multi Positional Cased 175 $414.00 Time Remaining: 16d 22h 36m Buy It Now for only: $414.00 |
 Fedders 30 Ton 14 Flush Width Cased A Coil R 22 AC1A036A14 $165.00 Time Remaining: 4d 12h 10m Buy It Now for only: $165.00 |
 4 TO 5 TON UPFLOW DOWNFLOW VERTICAL CASED EVAPORATORAC COILS 21 W X 30 H $409.99 Time Remaining: 10d 19h 52m Buy It Now for only: $409.99 |
 Haier Coil 3 Ton Multi Positional Cased 175 $378.00 Time Remaining: 16d 22h 36m Buy It Now for only: $378.00 |
 Goodman CACF 15 Ton Cased Indoor Coil Upflow Downflow R 22 Refrigerant Only $163.00 Time Remaining: 7d 20h 19m |
 Hvac Direct Coil 3 Ton Up Down Cased 14 $300.00 Time Remaining: 16d 22h 36m Buy It Now for only: $300.00 |
 NEW 35 TON CENTRAL AIR AC FULL CASE EVAPORATED COILS $399.99 Time Remaining: 21d 13h 30m Buy It Now for only: $399.99 |
 Haier Coil 4 Ton Multi Positional Cased 235 $414.00 Time Remaining: 16d 22h 36m Buy It Now for only: $414.00 |
 ASPEN CE48G44245L015 4 ton MULTI POSITION AC HP CASED A COIL R 410A 163197 $229.98 Time Remaining: 22d 14h 16m Buy It Now for only: $229.98 |
 Whirlpool 15 20 ton Horizontal Cased Coil $159.00 Time Remaining: 7d 20h 19m |
 Hvac Direct Coil 3 Ton Horiz Cased 175 $353.00 Time Remaining: 25d 9h 16m Buy It Now for only: $353.00 |
 Hvac Direct Coil 3 Ton Up Down Cased 175 $349.00 Time Remaining: 16d 22h 36m Buy It Now for only: $349.00 |
 Hvac Direct Coil 3 35 Ton Up Down Cased 245 $425.00 Time Remaining: 20d 3h 31m Buy It Now for only: $425.00 |
 Goodman CTPF 15 20 Ton Up Down Cased Coil $185.00 Time Remaining: 7d 20h 19m |
 Hvac Direct Coil 15 20 Ton Up Down Cased 14 $250.00 Time Remaining: 16d 22h 36m Buy It Now for only: $250.00 |
 Carrier 2 TON Cased Horizontal Coil CNRHP2417 $299.00 Time Remaining: 16h 40m Buy It Now for only: $299.00 |
 Hvac Direct Coil 4 5 Ton Up Down Cased 21 $428.00 Time Remaining: 20d 36m Buy It Now for only: $428.00 |
 20 TON FULL CASE EVAPORATED EVAPORATOR COILS R22 UPFLOW DOWNFLOW W TX VALVE $234.99 Time Remaining: 16d 12h 31m Buy It Now for only: $234.99 |
 Hvac Direct Coils 3 35 Ton Upflow Downflow Cased 245 $289.00 Time Remaining: 7d 20h 19m |
 R22 35 TON FULLY CASED EVAPORATOR COILS MULTI POSITION RIGHT HAND DRAIN $404.99 Time Remaining: 8d 12h 1m Buy It Now for only: $404.99 |
 15 Ton 13SEER R410A Condensing Unit Evap Cased Coil $834.00 Time Remaining: 19d 18h 40m Buy It Now for only: $834.00 |
 R22 4 TON CASED EVAPORATOR COILS MULTI POSITION 24 1 2 W x 20 1 2D x 32 1 4H $439.99 Time Remaining: 16d 14h 15m Buy It Now for only: $439.99 |
 3 TON FULL CASED MULTI POSITION R22 EVAPORATOR COILS LEFT HAND DRAIN $339.99 Time Remaining: 3d 16h 46m Buy It Now for only: $339.99 |
 Goodman Cased Indoor Upflow Downflow Application Coil CAPF3030D6 $212.00 Time Remaining: 7d 20h 19m |
 R410A 4 TON FULL CASED EVAPORATOR COILS MULTI POSITION RIGHT HAND DRAIN $429.99 Time Remaining: 14d 12h 40m Buy It Now for only: $429.99 |
 Hvac Direct Coil 3 35 Ton Horiz Cased 21 $355.00 Time Remaining: 26d 18h 35m Buy It Now for only: $355.00 |
 Aire Flo 3 Ton Lennox Cased Vertical Evaporator Coil AC36G1A $339.79 Time Remaining: 29d 8h 56m Buy It Now for only: $339.79 |
 Whirlpool 4 5 ton Horizontal Cased Coil $289.00 Time Remaining: 7d 20h 19m |
 R410A 2 TON FULL CASED EVAPORATOR COILS MULTI POSITION 17 1 2W x 20 1 2D $249.99 Time Remaining: 23d 14h 57m Buy It Now for only: $249.99 |
 R22 25 TON FULL CASED EVAPORATOR COILS MULTI POSITION $289.99 Time Remaining: 8d 12h 9m Buy It Now for only: $289.99 |
 Fedders 20 Ton 16 R22 Flush Width Cased A Coil AC1A024A16 $165.00 Time Remaining: 3d 23h 43m Buy It Now for only: $165.00 |
 R410A 3 TON FULL CASED EVAPORATOR COILS MULTI POSITION $379.99 Time Remaining: 21d 14h 42m Buy It Now for only: $379.99 |
 Whirlpool 3 ton Horizontal Cased Coil $249.00 Time Remaining: 7d 20h 19m |
 Hvac Direct Coil 15 20 Ton Horiz Cased 14 $294.00 Time Remaining: 20d 3h 31m Buy It Now for only: $294.00 |
 Haier Coil 25 Ton Multi Positional Cased 145 $323.00 Time Remaining: 16d 22h 36m Buy It Now for only: $323.00 |
 ADP HD53660D245B3103AP 5 TON AC HP HORIZONTAL CASED A COIL R 410A 163318 $377.00 Time Remaining: 3d 4h 30m Buy It Now for only: $377.00 |
 Central Air Conditioning A Coil Cased 3 Ton with Expansion Valve R410A Freon $359.00 Time Remaining: 8d 15h 14m Buy It Now for only: $359.00 |
 Goodman Cased Indoor Upflow Downflow Application Coil CAPF3636D6 $236.00 Time Remaining: 8d 11h 13m |
 15 TO 2 TON VERTICAL CASED EVAPORATOR COILS 21 W X 22 H UPFLOW DOWNFLOW $239.99 Time Remaining: 20d 16h 11m Buy It Now for only: $239.99 |
 R22 3 TON FULL CASE EVAPORATOR COILS MULTI POSITION 21 W x 20 1 2D x 28 3 4H $394.99 Time Remaining: 14d 11h 42m Buy It Now for only: $394.99 |
 R410A FULL CASED EVAPORATOR COILS MULTI POSITION 35 TON 17 1 2W x 20 1 2D $399.99 Time Remaining: 16d 13h 50m Buy It Now for only: $399.99 |
| Account limit of 2039 requests per hour exceeded. |
The Importance of Induction Coils in Telephone Equipment
In this article, I aim to cover the importance of the induction coil in getting the highest fidelity sound reproduction in telephone equipment. This may seem a rather pedantic point, but it is absolutely critical to ensure sound is reproduced correctly.
The size and quality of the iron core, the relation between the number of turns in the primary and secondary windings, and the mechanical construction of the induction coil are matters of the greatest importance, and have not in general received the attention which they merit.
A number of attempts have been made to calculate mathematically the best dimensions and resistances of the telephone induction coil, but the matter is of such an extremely complex nature, and all of the quantities are subject to such complex and indeterminate variations, that the results so far produced have been in general unreliable.
Only a few series of experiments are on record from reliable sources giving the results of comparative tests between induction coils of various dimensions.
It may be said that definite results from any such series of tests are extremely hard to get, as the quality and loudness of transmission is subject to a very great personal error, even in the case of experienced experimenters.
In making comparative tests of any telephone apparatus it is of the greatest importance that all possibility of prejudice on the part of the experimenter be removed, and in order to do this it is essential that he be in ignorance at all times of the particular instrument that he is testing. To illustrate this point, suppose that three transmitters are being compared with respect to determining the general talking qualities of each.
If the party at the receiving telephone, who is to judge of the hearing, desires that one of these instruments produces better results than the others, he is very sure, even though he be strictly honest with himself, to conclude at the end that that transmitter is by far the best ; unless, of course, there is a very marked difference between them.
For this reason he should be kept in ignorance of the particular transmitter in circuit with the line at any time, and should only be told when changes are made. It is well to have the instruments numbered, the party judging of the merits to be in ignorance of the transmitters to which those numbers refer.
It is also a somewhat difficult matter in comparing the clearness with which instruments transmit or reproduce speech to select proper subject matter to be transmitted.
It is unfair to the first instrument tested to repeat the same sentence or read the same matter in each case, for the reason that the listening party becomes more or less familiar with the matter to which he is listening, and therefore often catches words at the second or third reading which he fails to grasp at the first.
It is therefore better to read a selection from a certain article in the first test, and a continuation of the same matter in each successive test, so that the character of the matter read will be approximately the same in each case.
However, where several instruments are apparently of almost the same merit, and where the transmission is so good that all of the matter may be generally understood, it has been found that a better way is to prearrange a number of series of words, a different series to be read into each instrument under test. Care must be taken, in the selection of these words, that each series contains words of the same character.
To illustrate : suppose five instruments are to be tested. Five different series of words may be prepared, containing such words as the following :
sign rhyme dine fine mine
going rowing sewing mowing throwing
missile thistle whistle bristle gristle
etc. etc. etc. etc. etc.
Each list should contain about forty words ; and as the words in each series will be seen to differ from the corresponding words in the others to only a slight extent, no instrument can be said to have an easier list than the others. The first list should be read into the first instrument slowly enough for the receiving party to write them down. Then the second list is read to the second instrument, and so on.
Such words are difficult to distinguish, especially when there is no context, as is the case in reading an arbitrary list of words. The receiving party should be required to write down the words as he hears them, and the list which is most correct according to his notes will probably represent the work of the best instrument so far as clearness is concerned.
It is only by a consideration of such details as these, simple though they be, that an unbiased opinion can be formed as to the relative merits of telephone equipment.
Many elaborate experiments have been performed for arriving at the comparative merits of similar instruments depending on the quantitative measurements of the amplitude of vibrations, the amount of current, and similar quantities, but in the first place the apparatus and time for such measurements are available to but few, and in the second place it is doubtful if the results obtained are as reliable as those obtained by carefully following the above suggestions carefully.
By following these experiments carefully, telephone designers are able to make sure that we can understand each other clearly when making or receiving calls!
About the Author
Malcolm Blake is a telephone enthusiast who embraces the best of the golden age of telephones along with the modern era. He has written a number of articles about modern telephony, including advice on how to do a reverse number look up