Patent GB-471603-A (GB)
Title: Improvements in and relating to printing telegraph systems
IPC: H04L12/06
Filed: 1936-03-24
Abstract: 471,603. Telegraph exchange systems. NATIONALE TELEPHONUND TELEGRAPHEN-WERKE GES. March 24, 1936, No. 8799. Convention date, April 18, 1935. [Class 40 (iii)] An identification signal is sent automatically from the called station in response to a " Who are you? signal from the calling station, and the apparatus used for this purpose can also be operated manually for adding the sending station's signature at the end of a message. Preparation for sending and receiving. In the idle condition of the apparatus the marking battery e is connected to line L and marking current flows through the receiving relay ER so as to keep the armature er in the position shown. When the station is about to send, the motor M is started by closure of the key ET which connects the current-source D to the time switch ZS, so that the motor circuit becomes closed at zs3. While the motor is acquiring speed a code signal comprising spacing impulses followed by a stop impulse of marking polarity is sent to line for preparing the receiver circuits. During a spacing impulse the marking battery e is cut off by the opening of the sending contact skr, while the spacing battery E is connected to line L through contact ska. At the receiving station the armature er is reversed and relay EH (which at the sending station is cut off at zs2) pulls up and holds on for a time but is subsequently released by the opening of the contact th of a thermal switch TH. Meanwhile the magnet ZS pulls up through eh2; this magnet starts the motor M as at the sending station. The magnet SP pulls up through eh6 and zs2 and holds on ; this relay guards against the undesired operation of the sending apparatus at the receiving station. " Who are you ? " and identification signals. The " who are you ? " signal comprises a shift signal followed by a special signal, and at the sending station the depression of the appropriate keys causes the contacts zz, wd, respectively to be closed; relay WDV at the sending station pulls up and disables the answer-back-device transmitting contacts nskr, nska at the sending station, in order that these may not send impulses during the action of the local answer-back transmitter, which responds to the " who are you ? " signal but is thus prevented from affecting the line ; at the same time the premature sending of a message by contacts skr, ska is prevented by the disabling-contacts nha, nhr, which are actuated by the answer-back device. At the receiving station the " who are you ? " signal causes relay N to be energized and cause an identification signal to be sent by contacts nskr, nska. A warning lamp UL or bell KL indicates that the station is ready to receive. At the end of a message the sending station can send the identification signal as a signature to the message, by manual depression of a key with contacts unt1, unt2; but at the receiving station the key contact unt1 is ineffective owing to the energization of relay SP. Traffic-controlled switches. At every revolution of the distributer shaft of the transmitter or of the receiver, a contact zms or zml, as the case may be, is closed so that the slow-release magnet ZS is energized and the working circuits are kept in the operative condition. When signals have ceased for a predetermined time, however, relay ZS is de-energized, the motor M is cut off at zs3, and the circuits are restored by zs1 and zs2 to the resting condition. Failure of the paper supply operates switch pap to ring the alarm KL. Testing. A key PT when depressed converts the double-current transmitter into a singlecurrent transmitter, the spacing battery E being cut off at pt3 while the printer magnet EM is in circuit with the mark-sending contacts skr, nskr, and with battery connections at er and zs2. The test key at pt4 cuts the line L off from the transmitter and applies to it the marking battery e, so that signals from the transmitter go to the local receiver only ; but an incoming signal received by armature er while the test is in progress energizes relay EH so as to close the alarm circuit at ehs.