Timeline of the telephone

Early months of 1879: The Bell Telephone Company is near bankruptcy and desperate to get a transmitter to equal Edison's carbon transmitter.
17 February 1879: Bell Telephone merges with the New England Telephone Company to form the National Bell Telephone Company. Theodore Vail takes over operations.
1879: Francis Blake invents a carbon transmitter similar to Edison's that saves the Bell company from extinction.
2 August 1879: The Edison Telephone Company of London Ltd, registered. Opened in London 6 September 1879.
10 September 1879: Connolly and McTighe patent a "dial" telephone exchange (limited in the number of lines to the number of positions on the dial.).
1879: The International Bell Telephone Company (IBTC) of Brussels, Belgium was founded by Bell Telephone Company president Gardiner Greene Hubbard, initially to sell imported telephones and switchboards in Continental Europe.[13][14]  International Bell rapidly evolved into an important European telephone service provider and manufacturer, with major operations in several countries.
19 February 1880: The photophone, also called a radiophone, is invented jointly by Alexander Graham Bell and Charles Sumner Tainter at Bell's Volta Laboratory.[15][16] The device allowed for the transmission of sound on a beam of light.
20 March 1880: National Bell Telephone merges with others to form the American Bell Telephone Company.
1 April 1880: world's first wireless telephone call on Bell and Tainter's photophone (distant precursor to fiber-optic communications) from the Franklin School in Washington, D.C. to the window of Bell's laboratory, 213 meters away.[17][18]
1 July 1881: The world's first international telephone call is made between St. Stephen, New Brunswick, Canada, and Calais, Maine, United States.[19]
11 October 1881: The Sydney telephone exchange opened with 12 subscribers.
1882: A telephone company—an American Bell Telephone Company affiliate—is set up in Mexico City.
14 May 1883: The Adelaide exchange was opened, with 48 subscribers.[12]
7 September 1883: The Port Adelaide exchange was opened, with 21 subscribers.[12]
4 September 1884: Opening of telephone service between New York and Boston (235 miles).[20]
3 March 1885: The American Telephone & Telegraph Company (AT&T) is incorporated as the long-distance division of American Bell Telephone Company. It will become the head of the Bell System on the last day of 1899.
1886: Gilliland's Automatic circuit changer is put into service between Worcester and Leicester featuring the first operator dialing allowing one operator to run two exchanges.
1887: Tivadar Puskás introduced the multiplex switchboard, that had an epochal significance in the further development of telephone exchange.[21]
13 January 1887: the Government of the United States moves to annul the master patent issued to Alexander Graham Bell on the grounds of fraud and misrepresentation. The case, known as the 'Government Case', is later dropped after it was revealed that the U.S. Attorney General, Augustus Hill Garland had been given millions of dollars of stock in the company trying to unseat Bell's telephone patent.
1888: Telephone patent court cases are confirmed by the Supreme Court, see The Telephone Cases
1889: AT&T becomes the overall holding company for all the Bell companies.
2 November 1889: A.G. Smith patents a telegraph switch which provides for trunks between groups of selectors allowing for the first time, fewer trunks than there are lines, and automatic selection of an idle trunk.
10 March 1891: Almon Strowger patents the Strowger switch the first Automatic telephone exchange.
30 October 1891: The independent Strowger Automatic Telephone Exchange Company is formed.
3 May 1892: Thomas Edison awarded patents for the carbon microphone based on applications lodged in 1877.
18 October 1892: Opening of telephone service between New York and Chicago (950 miles).[20]
3 November 1892: The first Strowger switch goes into operation in LaPorte, Indiana with 75 subscribers and capacity for 99.
30 January 1894: The second fundamental Bell patent for the telephone expires; Independent telephone companies established, and independent manufacturing companies (Stromberg-Carlson in 1894 and Kellogg Switchboard & Supply Company in 1897).
30 December 1899: American Bell Telephone Company is purchased by its own long-distance subsidiary, American Telephone and Telegraph (AT&T) to bypass state regulations limiting capitalization. AT&T assumes leadership role of the Bell System.
25 December 1900: John W. Atkins, the manager at International Ocean Telegraph Company (IOTC), a subsidiary of Western Union Telegraph Company made the first international telephone call over telegraph cable at 09:55am from his office in Key West to Havana, Cuba.[22] Atkins was reported in the Florida Times Union and Citizen as saying, "For a long time there was no sound, except the roar heard at night sometimes, caused by electric light current." He continued calling Cuba and finally came back the words, clear and distinct: "I don't understand you."[23]
27 February 1901: United States Court of Appeal declares void Emile Berliner's patent for a telephone transmitter used by the Bell telephone system
1902: The first Australian interstate calls between Mount Gambier and Nelson.[12]
26 February 1914: Boston-Washington underground cable commenced commercial service.[20]
16 January 1915: The first automatic Panel exchange was installed at the Mulberry Central Office in Newark, New Jersey; but was a semi-automatic system using non-dial telephones.
25 January 1915: First transcontinental telephone call (3600 miles), with Thomas Augustus Watson at 333 Grant Avenue in San Francisco receiving a call from Alexander Graham Bell at 15 Dey Street in New York City, facilitated by a newly invented vacuum tube amplifier.[24]
21 October 1915: First transmission of speech across the Atlantic Ocean by radiotelephone from Arlington, Virginia to Paris, France.[20]
1919: The first rotary dial telephones in the Bell System installed in Norfolk, Virginia. Telephones that lacked dials and touch-tone pads were no longer made by the Bell System after 1978.
1919: AT&T conducts more than 4,000 measurements of people's heads to gauge the best dimensions of standard headsets so that callers' lips would be near the microphone when holding handsets up to their ears.[25]

Question: When were telephones first used in homes?