Patent GB-856935-A (GB)
Title: Improvements in or relating to recording systems
Inventor: COMYN FRANK EDGAR
IPC: H04M11/10
Filed: 1957-04-23
Abstract: 856,935. Centralized dictation systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. April 23, 1957, No. 12853/57. Addition to 747,425. Class 40 (4). An automatic telephone-exchange system having one or more recording means directly accessible to subscribers, means being provided at subscriber's stations for controlling the recording means over the speech path, and means being provided to prevent the playback to one subscriber of signals recorded by another subscriber, as claimed in the parent Specification, is characterized in that only when the recording means is conditioned for the recording of speech signals, and regardless of whether or not speech signals are actually being recorded, a low-level alternating current signal is recorded on the recording medium, further means being effective during the re-wind operation to detect the absence of such low-level signal and thereupon to terminate the re-winding operation. When a subscriber dials an appropriate code the recording set is seized by operation of relays A and B and lamp LP1 lights. QR and BR energize, the latter supplying tone from TG to the line. The secondary of transformer TR applies a voltage alternating between earth and - 50v. to relays P and Q. Momentary operation of key K1 by the subscriber therefore energizes P which causes a low-level A.C. signal to be applied through resistor VR1 to lead 10 and is recorded on the tape. SW pulls up slowly and operates amplifier switching relay ASA and XA, which drives the tape in a forward direction to record signals from leads RL. The tape passes an erase head just before the recording head. SW also restores QR and disconnects the tone generator TG from the line. The subscriber now dictates his message. To stop recording the subscriber operates key K2 momentarily to operate Q which restores SW. Relays ASA and XA restore to stop the tape and re-connect tone generator TG to the line. When the key K2 is released P and Q fall back. Before the tape stops a small portion passes the recording head and records only the low-level A.C. signal. Reproduction of recorded message. If the subscriber depresses key K3, Q pulls up to operate SW slowly, so that XA and YA energize to reverse the tape quickly, the subscriber hearing the resultant noise. When the subscriber releases key K3, Q and YA restoring, D operating momentarily and XA falling back and then energizing again. The tape then runs in the forward direction again. If the subscriber wishes to correct his message he operates key K1 to render the recording head effective. If he wishes to hear the whole of his message he holds K3 down until the re-wind noise is replaced by tone from TG. The low-level A.C. signal preceding the start of the message. The absence of a signal on lead 10 causes V1 to conduct, FA to operate and SA to restore. Relay FA energizes QR, returns tone from TG to the subscriber. XA and YA fall back to stop re-wind. Release of key K3 restores Q, whereupon D pulls up slowly, cuts off V1 so that FA restores, and re-operates XA so that the tape runs forward again. When there is again no signal on lead 10 because the end of the message has been reached, V1 conducts again to reoperate FA and release SA. TG is again audible to the subscriber and XA releases to stop the tape. If the subscriber wishes to continue his message the tape is returned a short distance to eliminate the portion with no recorded signals. Momentary operation of key K1 causes P, RS, YA, FA to energize. RS disconnects the low-level A.C. signal from lead 10. Release of FA disconnects tone generator TG and operates XA. XA and YA then reverse the tape until the end of the recorded message is encountered when SA re-operates to restore YA. XA then causes the tape to run forward a short distance with the reproducing head still effective until the end of the previously recorded message is reached when SA falls back. RS falls back to operate ASA so switching the amplifier to recording condition. When the subscriber clears a considerable gap is made on the tape without signals to prevent intrusion by another subscriber. If the subscriber wants the attendant he dials a further code. The attendant's speech wires AC are connected to line when he operates key K4.