| 1938 UNION SWITCH SIGNAL CO Railway Signaling |
| 1938 GEORGE MELLEN Signal Device Patent Print |
| 1938 GAYNOR Audible Electric Signal Patent Print |
| 1938 SMALL Basketball Signal Apparatus Patent |
| 1938 UNION SWITCH SIGNAL CO Electrical Relay Art |
| 1938 GEN RAILWAY SIGNAL CO Train Describer System |
| 1938 UNION SWITCH SIGNAL CO Railway Signaling System |
| 1938 GODCHAUX LEON Signal RICHARD C LUHMAN Art |
| 1938 RICHARD C LUHMAN Signal Patent Print Art |
| 1938 SCHWARZE ELECTRIC Chime Signal Art Print |
| 1938 GEN RAILWAY SIGNAL CO Railway Signaling System |
| 1938 RITTENHOUSE ARTHUR Signal Device Patent |
| 1938 AKERS EARL Signal Switch Patent Print Art |
| 1938 LITTLE FRODERICK Signal Device Patent Print |
| 1938 GEN MOTORS CORP Sound Signal Patent Print |
| 1938 UNION SWITCH SIGNAL CO Railway Switch Operating |
| 1938 UNION SWITCH SIGNAL CO Railway Switch Controlling |
| 1938 ADUS Signal Tool Paging Unit System Patent 41232 |
| 1938 GEN RAILWAY SIGNAL CO Railway Track Circuit Relay |
| 1938 GOERTZEN Float With Signal Lamp Patent |
| 1938 GEN RAILWAY SIGNAL CO Alternating Current Relay |
| 1938 SIMPSON THORNTON Highway Signal Patent |
| 1938 HAINES Highway Crossing Signal Railways Art |
| 1938 CALVERT Coin Signal TOWNSEND Patent 20029 |
| 1938 UNION SWITCH SIGNAL CO Track Rail Contactor |
| 1938 MYRTLE R WORKMAN Basketball Signal Art |
| 1938 CONDON Automobile Signal Switch Patent |
| 1938 UNION SWITCH & SIGNAL CO Light Signal Art |
| 1938 UNION SWITCH SIGNAL CO Remote Indication |
| 1938 UNION SWITCH SIGNAL CO Signaling Art Print |
| 1938 WELLS WESLEY Light Signal Patent Print Art |
| 1938 UNION SWITCH SIGNAL CO Interlocking Control |
| 1938 GEN RAILWAY SIGNAL CO Railway Track Circuit |
| 1938 GEN RAILWAY SIGNAL CO Signaling System Railroads |
| 1938 WESTERN Controlling A Waving Crossing Signal |
| 1938 UNION Highway Crossing Signal Railways Art |
| 1938 CRITCHFIELD Sounding Signal Device Patent |
| 1938 UNION SWITCH SIGNAL CO Interlocking Relay |
| 1938 GEN RAILWAY SIGNAL CO Track Circuit Patent |
| 1938 UNION SWITCH SIGNAL CO Railway Track Circuit |
| 1938 WALTER Controlling A Waving Crossing Signal |
| 1938 VON VOIGTLANDER Chime Signal Patent Print |
| 1938 A E RITTENHOUSE CO INC Signal Device Patent |
| 1938 GEN Highway Crossing Signal System Art |
| 1938 DORSCHEL Highway Crossing Signal System Art |
| 1938 UNION SWITCH SIGNAL CO Speed Responsive |
| 1938 CRITCHFIELD ROBERT Sound Signal Patent |
| 1938 UNION SWITCH SIGNAL CO Light Sensitive Art |
| 1938 GEN RAILWAY SIGNAL CO Track Circuit Railroads |
| 1938 GEN MOTORS CORP Sounding Signal Art Print |
| 1938 Union Switch & Signal Ad: Make Time Savings |
| 1938 General Railway Signal Ad: NX System Cuts Costs |