................................. Fig. 215.—Building up a Fixed Condenser. .......................... Fig. 216.—A Fixed Condenser enclosed in a Brass Case made from a Piece of Tubing fitted with Wooden Ends. .......................... Fig. 217.—A Telephone Head Set. ................................... Fig. 218.—A Circuit showing how to connect a Double-Slider Tuning Coil. ............................................................. Fig. 219.—Circuit showing how to connect a Loose Coupler. ......... Fig. 220.—A Diagram showing how to connect some of the Instruments described in this Chapter. ........................................ Fig. 221.—A Wireless Spark Coil. .................................. Fig. 222.—Small Spark Gaps. ....................................... Fig. 223.—Diagram showing how to connect a Simple Transmitter. .... Fig. 224.—A Test-Tube Leyden Jar. ................................. Fig. 225.—Eight Test-Tube Leyden Jars mounted in a Wooden Rack. ... Fig. 226.—A Helix and Clip. ....................................... Fig. 227.—An Oscillation Transformer. ............................. AN OSCILLATION HELIX. ............................................. AN OSCILLATION CONDENSER. ......................................... Fig 228.—Circuit showing how to connect a Helix and a Condenser. .. Fig 229.—Circuit showing how to connect an Oscillation Transformer and a Condenser. .................................................. Fig 230.—An Aerial Switch. ........................................ Fig 231.—A Complete Wiring Diagram for both the Transmitter and the Receptor. ......................................................... Fig. 232.—The Continental Alphabet. ............................... Fig. 233.—A Coherer and a Decoherer. .............................. Fig. 234.—Details of the Coherer. ................................. Fig. 235.—The Relay. .............................................. Fig. 236.—The Complete Coherer Outfit. ............................ Fig. 237.—A Simple Arrangement showing the Inductive Action between two Coils. ........................................................ Fig. 238.—A Simple Wireless Telephone. Speech directed into the Transmitter can be heard in the Receiver, although there is no direct electrical connection between the two. ..................... Fig. 239.—A Double-Contact Strap-Key. The Dotted Lines show how the Binding-Posts are connected. ...................................... Fig. 240.—The Circuit of the Wireless Telephone. When the Key is up, the Receiver is ready for Action. When the Key is pressed, the Transmitter and Battery are thrown into the Circuit. .............. Fig. 241.—A Complete Wireless Telephone and Telegraph Station for Amateurs. 1. The Telephone Coil. 2. The Telephone Transmitter. 3. Double-Contact Strap-Key. 4.