Subscribers Telegraph System

a form of electronic communication between subscribers (enterprises, institutions, organizations) by way of direct two-way exchange of telegraph messages. The subscribers’ telegraph system in many ways resembles ordinary telephone communication, but has certain advantages: the messages are sent and received (even if the receiver is not present) in written form; and the use of the frequency telegraph method makes it possible to have a great number of telegraph channels on one trunk telephone line, which lowers the price of subscribers’ communication. Direct communication between subscribers greatly reduces the time of written intercourse as compared with the time needed if telegrams are handled by communication enterprises, delivered to the addressees, and so forth.

Communication between subscribers is provided by a manual (ATR) or automatic (ATA) subscribers’ telegraph exchange; on the subscriber end is a coil start-stop apparatus with an automatic answer-back device and a call instrument, which are connected to the exchange by a two-wire line (usually a pair of conductors of a telephone cable).

Instead of manual switchboards, whereby the telegraph operator connects the subscribers with individual jacks, the automatic subscribers’ telegraph system has crossbars with telephone selectors that connect the subscribers automatically; the subscriber’s call instrument has a dial similar to a telephone dial.

The subscribers’ telegraph system (Telex) appeared abroad (in the USA, Britain, Germany) in the early 1930’s. Two methods are used for transmission: with DC and AC voice frequencies. With the first method, used in the Federal Republic of Germany, the German Democratic Republic, Sweden, and other countries, the subscriber has only a telegraph device (teletype) and a call instrument, which are connected to the subscribers’ telegraph exchange by a separate two-conductor line. The second method, used in the United States, utilizes the telephone network. The subscriber’s telegraph apparatus has a voice-frequency attachment that transforms the incoming DC pulses into AC pulses (which transmit farther through a telephone line) and back into DC upon reception. The USSR mainly uses the DC subscribers’ telegraph system.

In 1947 the Central Telegraph Exchange in Moscow installed the first ATR exchange for 30 numbers (subscribers’ lines) to transmit messages from Moscow telegraph divisions directly to telegraph offices of other cities. This exchange was later replaced by a manual exchange for 240 numbers, and later by an automatic exchange. After 1950, manual subscribers’ telegraph exchanges with as many as 80 numbers were installed (ATR-20, ATR-40, ATR-60, ATR-80), as well as the ATA-50 with 100 subscriber and 60 intercity lines for oblast and republic telegraph communication. In 1957 a device for the automatic recording of conversation costs (ATA-57) was added to the ATA-50 exchange. By 1968 such exchanges operated in more than 150 cities. Raion communication centers widely use an ATA-M exchange with ten subscriber lines with automatic coupling that provide communication with subscribers of other exchanges through three intercity telegraph channels. By 1968 more than 800 such exchanges were in operation. The total number of subscriber telephone installations in the country surpassed 14,000 in 1968.

The further development of the network of the subscribers’ telegraph system is directed at replacing the electromechanical rotary step and step-by-step decimal selectors having sliding contacts with the more reliable and precise crossbar switches having contact pressure. A model of the automatic exchange ATA-K coordinate system with 90 subscriber and 40 intercity lines has been successfully in operation at the telegraph office in the city of Kherson since 1967.