| 摘要 |
1,251,307. Facsimile transmission system. XEROX CORP. 22 Dec., 1969 [23 Dec., 1968], No. 62307/69. Heading H4K. A facsimile transceiver is coupled to a data modem attached to a telephone line by means of a logic circuit which includes a timing device for cutting-off the data modem as soon as the transmission of a facsimile signal has ceased. Cessation of the signal may occur in respect of an incoming transmission or an outgoing transmission or a lack of e.g. paper in the transceiver which effectively prevents further reception. Operation, automatic.-An operator places the data modem (not shown) in its data mode and closes switch 14 thus connecting input a of NAND gate 10 to ground i.e. logic 0. Provided paper is available in the facsimile transceiver (not shown), logic 1 appears on lead " Paper " so that " O " appears on the b input of NAND gate 30. The consequential " 1 " outputs of gates 10 and 30 together with the " 1 " output of inoperative manual switch 18 cause NAND gate 12 to produce a " 0 " output which is effective to light Auto lamp 16 and to bring-up relay K1. The latter indicates to the data modem over lead " Ready " that the system is ready for a facsimile transmission. In the case of an incoming call, a " 1 " appears on lead " Interlock " from the data modem whereby input c of NAND gate 92 is also marked with a " 1 ". The input a of gate 92 is already at " 1 " and its input b will receive " 1 " from NAND gate 40 provided there is no incoming facsimile signal i.e. " 0 " on the " Carrier Detect " lead. Consequently the " 0 " output of gate 92 turns on timer 90 which, if it times-out in say 30 secs., operates relay K2 and thus causes the data modem to hang-up. If, however, a facsimile signal does appear, the output of gate 40 changes to " 0 " and via gate 92 resets the timer. The continuation of the lead " Carrier detect " past inverters 50, 60 is effective to control the transceiver. If the transceiver runs out of paper, the resultant " 0 " on lead " Paper " is immediately passed via gate 40 so as to restart the time-out period and thus hang-up the data modem. In this case, relay Kl is also dropped via gates 30, 12 so as to prevent the data modem being seized again. In the case of an outgoing call a similar sequence of events takes place but release of the connection is controlled by the appearance of " O " on the " Paper " lead so that only one automatic send operation is allowed due to the release of K1. In the manual mode, the switch 18 is closed so that NAND gate 12 cannot activate K1. |
