were installed, but occasionally an editor would consider his time of sufficient value to justify the increased outlay of $10 a year for a 'second telephone.'
Following the now famous experiments with his telephones at the Centennial, Alexander Graham Bell had displaced the parchment or membrane diaphragm with one of iron, and brought out the wooden hand telephone to take the place of the oblong box, so inconvenient for general use. Then, in December, 1877, a few long rubber-encased hand telephones similar in form to the present receiver were sent out to several exchanges as an experiment. On July 1, 1878, Mr. Coy had 230 mahogany hand telephones, about 100 rubber hand telephones
and a dozen box telephones. But this rubber hand telephone did not go into general use until the summer of 1878, and, in some exchanges, never really supplanted the original wooden hand telephone, the earlier magneto sets doing so.
Meanwhile an improved form of the oblong box telephone, shown in a previous chapter, was brought out in June, 1877, but met with no favor, as it also required a table or a shelf for its support in a horizontal position. In August, 1877, came the first of the oblong box telephones remodeled so as to be fastened to the wall in a vertical position (Fig. 23). The only telephone circuits in those days were private and social lines, the first commercial exchange opening in January, 1878, and users of projected private lines did not take kindly to this innovation, preferring to have the more convenient hand telephone which could so easily be shifted from lips to ear. And this was the prevailing sentiment even after exchanges were in operation. Thus this upright form of box telephone did not come into general use until the winter of 1878-79, when it served only as part of a subscriber's set.
In the autumn of 1878, the parent Bell company brought out the first of the many forms of magneto bell telephone sets. This early type of wall set (Fig. 24) had the rubber-encased hand telephone hung from a hook projecting through the door on the front of the box. The attaching of two hand telephones to the magneto to serve