162 BELL SYSTEM TECHNICAL JOURNAL 



two-wire telephone line corresponds to the "X" arm of the bridge 

 and the balancing artificial line to the " Y" arm. The ratio arms are 

 in effect formed by the windings of the hybrid coil. 



Speech Received from Ship Re-Transmitted from 

 Shore Station 



Now this junction circuit always has some unbalance because it 

 is obviously impossible to maintain a perfect symmetry between 

 the telephone line and the balancing network. Especially is this 

 true where the telephone line is a type not designed for repeater 

 operation and is switched at its terminal to any of a number of lines 

 of different impedances, as was the case with the circuit used in the 

 tests. 



This unbalance between the line and its balancing network will 

 be seen to permit some of the speech-current received over the radio 

 link to get across into the transmitting circuit, to modulate the shore 

 station carrier and to get out into the ether again on the transmitting 

 wave length. As a matter of fact during the experiments the unbalance 

 was sometimes such as to permit of fairly strong transmission around 

 back thru the shore transmitter, so that incoming speech was repeated 

 out thru the shore station transmitter in amplified form. This en- 

 abled listeners in the vicinity of New York to hear the conversation 

 originating on the ship almost as well as that originating on land, 

 and they naturally thought that they were picking up the ship's 

 radio transmission directly, whereas they were acfiually overhearing 

 the re-transmission of the shore-station's reception. 



The Thru Circuit as a Repeated Telephone Circuit 



This re-transmission makes all the more evident the true role of 

 the shore station, namely, that of a large telephone repeater between 

 two sections of line, the one a land line and the other a "space" 

 line, and functioning also to convert between the voice frequencies 

 of one section and the radio frequencies of the other. As such, we 

 can consider the over-all circuit from a transmission standpoint much 

 as we do long distance repeated telephone circuits. 



Now one of the most important transmission considerations in 

 such a long distance circuit is that of how the amplification is ap- 

 plied in relation to the losses in the circuit. This question of amplifi- 

 cation is particularly important in the ease of combination radio-wire 

 systems, because the radio circuit possesses inherently large trans- 

 mission losses and requires correspondingly large amplification. The 



