Belgium 83 



the microphone, transmitter battery, and the top stop of a Morse 

 key K. When this is depressed it closes the circuit of the ringing 

 battery B, and by making and breaking contact impulses are sent 

 into line by induction to the secondary coil sufficiently powerful 

 to start the phonic relay at the distant station. The wires (one 

 pair of which is shown at ci 02) coming from the local table end 

 in plugs FI F2, of which FI is an ordinary single plug, while F2 

 has a metallic tip insulated from the piece which is in connection 

 with the cord. This tip brings a and b into contact when inserted 

 in J3, and so closes the translator secondary circuit. FI rests on 

 a metallic earth strip when out of use. On the phonic relay in- 

 dicating a call, the operator depresses D and is then enabled both 

 to ring and speak to trunk. If the connection demanded is with 

 a single-wire subscriber the insertion (after the necessary com- 

 munication with the local operator) of F2 in J3 completes it, since 

 by this movement the translator secondary is brought into use 

 through the contacts a and b, while the junction wire C2 utilised 

 for the connection finds circuit through the main contact of F2, 

 the socket of J3, primary TP of translator, and earth. The phonic 

 relay PI P2 remains in shunt (key D being up) across the loop and 

 serves as ring-off. Two metallic circuits are joined direct by in- 

 serting a double-conductor cord terminating in two single plugs 

 at each end in the jacks ji J2 and the corresponding jacks of the 

 second metallic circuit. The indicator M between the earth stop 

 of FI and earth serves for calling from the local to the trunk 

 operator ; the latter has also a battery push or generator for calling 

 the former. There can be no doubt of the superiority of this 

 plan over that in use at Brussels, since there are no coils to speak 

 through, while the contacts are fewer and the arrangements 

 simpler in every way. M. Delville evidently understands that in 

 telephony, as in most things, the shortest road with nothing to 

 jump over is the best. 



Several patterns of phonic relay are used. One of the best 

 that designed by M. Sieur, is shown in fig. 20. It consists of two 

 coils P having soft-iron cores polarised by the permanent magnet 

 M. A soft-iron diaphragm D placed in front of, and close to, the 

 cores, is furnished with a platinum disc d, on which rests the light 

 metal hammer H provided with an adjustable counterpoise A, by 



G 2 



