Patent GB-849379-A (GB)
Abstract: 849,379. Printing-telegraph systems. TELEREGISTER CORPORATION. Sept. 2, 1958 [Sept. 12 1957], No. 28119/58. Drawings to Specification. Class 40(3). In a telegraph system having a main station and a number of subsidiary, or way stations connected in a line circuit with transmitting and receiving equipment at the various stations, characteristic message invitation signals are transmitted to invite the way stations to transmit messages to the main station on a predetermined sequential cyclic basis, means preferably at the main one of the said stations initiates an invitation cycle by transmitting an invitation signal allotted to one of said way stations and the last named way station has means which selectively responds to its allotted invitation signal to transmit to the way circuit an invitation signal individual to a succeeding way station. The system is such that if an invited way station has no message to transmit, that station automatically sends the invitation signal for the next way station, If, however, the way station has a message to transmit to the main station, the latter station at the end of the message transmits the invitation signal for the next way station in the call sequence. The system may be arranged to exclude some stations from the cycle, and if a station without any message to transmit sends the invitation signal for the subsequent way station which has been closed out, this signal is detected by the main station which automatically sends the invitation signal for the station next in sequential order after the excluded station. The wayside stations, depending on their amounts of message traffic, may be invited to send a number of separate messages when operatively connected in the transmission circuit during a call cycle and a way station with less than its alloted number of messages for transmission to the main station operates automatically to send the invitation signal for the next station in the call cycle. The way stations may send keyset or numerical information to be fed to a computer at the main station and this may cause corresponding information to be passed to a suitable receiving device at the way station. The information is preferably sent in a 4-unit binary code which is subjected to an "odd-mark" parity check at the main and subsidiary stations. The teleprinter or keyset traffic is always preceded by a significant message start character different for the two types of traffic, and which is effective to cut out the control circuits of the way stations other than that which has been selected for communication with the main station. Also when any way station has signalled by opening the line circuit that it has a message for the main station, a temporary lock out of the wayside station control circuits is effected until the invitation cycle has been initiated by the main. station. The end-of-message signal for the last station of the cycle is the line-feed signal, and if any of the way station has transmitted to the main station, the latter, in response to the reception of the l.f. signal initiates a further invitation cycle. If however, none of the way stations has transmitted to the main station, the latter operates to remove the lock out of the way stations, and an automatic timing device initiates an invitation cycle after about 10 minutes, unless a request from a way station in the interval has caused the main station to inaugurate an invitation cycle. U.S.A. Specification 1,805,374 is referred to.