Patent EP-0148406-B1 (EP)
IPC: H04M11/08
Filed: 1984-12-03
Granted: 1989-03-22
Abstract: 1. Telephone equipment with a subscriber set (1, 2) for the interrogation of information, for the putting-in of replies and for the generation of communications of digitally coded kind for a technical text communication service, in which the text data modulated by a low-frequency carrier are transmitted by way of telephone lines (36), with one or more telephone terminals in connection with a telephone instrument (3, 4), by way of which telephone conversations are conductible in parallel with the text communications operation by way of further lines or in place of the text operation by way of a common line, characterised thereby, that a data transmission device (22) (modem) is implemented in the subscriber set (1 or 2) or is functionally connected with this and connected by way of at least one data transmission line (23), one data input line (24) and one control signal line (34) with a decoding circuit (31) for the preparation of the data for the visual representation or for the editing of texts, which decoding circuit (31) on the actuating of a function setter (35) delivers a control signal by way of the control signal line (34) for the preparation of the data transmission operation, which data transmission device (22) converts the digitally coded serial direct current binary signals into frequency-modulated low-frequency signals and issues them or converts frequency-modulated low-frequency signals, which arrive from an image screen text exchange (16) or either from another subscriber or from a data bank, such as external computers (17), into serial direct current binary signals processable by the decoder circuit (31) for the text representation, that the data transmission device (22) is connected by way of a change-over switch (6) with the telephone line (36), by way of which a telephone instrument (3 or 4) is connectible by a dialling equipment for the establishment of a line connection or for the conduction of a telephone conversation, which change-over switch (6) connects the telephone line (36) with the telephone instrument (3) in dependence on a switching signal (S), which is put out by the dialling equipment at the latest on the emission of the dialling pulses, insofar as the speech line (36) is freed and neither a speech nor a data line connection exists, that the switch (6) after the establishment of the connection is switchable over constrainedly by a control signal (carrier) dependent on the data operation and connects the data transmission device (22) with the telephone line (36), that the switch setting of the switch (6) assumed during the data transmission remains maintained also after termination of the data transmission until the renewed establishment of a connecting line and that the change-over switch (6, 7) on a call by another subscriber (1 or 2) applies the telephone instrument (3, 4) to the telephone line (36) and thereby frees the connection for the speech operation when no control signal (carrier), which signals the data transmission operation or is associated therewith, from the caller (1 or 2) is present in a certain time interval after the dialling.