| Year | 1921 |
| Date | 15-Sep |
| Volume | 45 |
| Issue | 1,064 |
| Page | 213 |
| Category | Electronic |
| Part | |
| Title | Spark Coils for Wireless Telegraphy |
| Author | J.P. |
| Notes | Building up the secondary, type of terminal, complete spark coil, discharging rods for testing purposes, mercury break or interrupter, mounting and finishing - breaks, commutator, circuit from primary of coil, conclusion |