Fig. 249.—Handles and needles of telegraph.
Fig. 250.—Telegraph wires.
Fig. 251.—Insulator.
The Telegraph Alphabet, in the two-needle instrument, now not generally used in England, is given below.
| Two-Needle Alphabet. | |||
|---|---|---|---|
| Movements of First Needle. | Of Second Needle. | Of both Needles. | |
| A | is signified by moving needle once to right | ||
| B | once to left | ||
| C | By moving needle once to right | ||
| D | once to left | ||
| E | Moving to right. | ||
| F | Moving to left. | ||
| G | twice to right | ||
| H | twice to left | ||
| I (or J) | Twice to right | ||
| K | Twice to left | ||
| L | Twice to right. | ||
| M | Twice to left. | ||
| N | One to right, one to left | ||
| O | One to left, one to right | ||
| P | One to right, one to left | ||
| O | One to left, one to right | ||
| R | One to right, one to left. | ||
| S | One to left, one to right. | ||
| T | Two to right, one to left | ||
| U | One to right, two to left | ||
| V | Two to right, one to left | ||
| W X | One to right, two to left | ||
| Y | Two to right, one to left. | ||
| Z | One to right, two to left. | ||
In the single needle instrument the letters are indicated by right and left vibrations, from A one right, to B one right and left, and so on, increasing to Z. This mode is now generally used.
The manner in which the current passes is shown by the following illustrations (figs. 252, 253).