Patent GB-814129-A (GB)
Title: Apparatus for the recording and reproduction of sound at a distance
IPC: H04M11/10
Filed: 1955-10-21
Abstract: 814,129. Centralized dictation systems. ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE CHARLEROI. Oct. 21, 1955 [Oct. 25, 1954], No. 30151/55. Class 40 (4). A single recording and reproducing machine E, Fig. 1, is available for use by any one of n sub-stations P1 ... Pn. At a central control station C, a gas discharge tube Vt strikes when power is switched on. Tubes V10 ... Vn0indicate which one, if any, of the sub-stations is busy using the machine. When the recording and reproducing head nears the end of the record track, a tube Vf gives a visible warning at the control station and a sound emitter X, Fig. 2, gives an audible warning at the busy substation. A tube V3 in the handset C1 at the substation conducts when the apparatus is set for recording. Record and repeat-back switches are provided on the handset which comprises an element Y serving as both a microphone and a loud-speaker. Tubes V1, V2 in the table set indicate respectively, when " on," that the machine E is free and that it is in action. Circuit arrangements. At the control station C, Fig. 3, each sub-station is allotted a multicontact relay only two such relays R, T for station P1, P2 being shown. Relay contacts are connected in a chain so that when one relay pulls up, it disables the other. Corresponding terminals of junction boxes B1, Fig. 2, and B1, Fig. 3, are connected to link the sub-station to the control circuit. The machine E is not described. In junction box A, terminals a, bare connected to a power supply. The record is driven when battery is disconnected from terminal C. Terminal d is connected in E to a contact which is closed when the track is near the end and completes a circuit over lead M. Recording takes place when battery is connected to terminal f. The return movement mechanism for the recording and reproducing head is controlled over terminal g. The combined microphone and loud-speaker is connected to the head over terminals h, i. Operation. When switch i0 is closed, battery is provided on lead 31 and an indication is given by tube Vt. When the machine E is not in use, tube V2 is sub-station P1, Fig. 2, conducts. When the handset is lifted contact s1 closes, V2 extinguishes and V1 strikes. Relay R pulls up in a circuit over terminals 2, 3 and contacts of both relays R, T and then locks to ground over r5. Tube V10 connected across the relay winding gives an indication that the sub-station P1 is busy. Contact i1 at sub-station P1 is changed over to transfer the battery on terminal 3 from contact c to contact f in box A and thereby to start recording, an indication being given by tube V3 which strikes. If switch i1 is restored and i2 is changed over, an impulse is transmitted by condenser C3, Fig. 3, over terminal g to step back the reproducing head. The record feed continues so long as either of switches i1, i2 is off normal. The instrument Y is connected to the machine E over terminals 6, 7 in boxes B1, B1<SP>1</SP> and over terminals h, i in box A. A repeater O may be connected between Y and box B1. End of track signal circuit, Fig. 4. A condenser C6 is normally charged to battery potential when the recording and reproducing head nears the end of the record track, a contact (not shown) closes a circuit over terminal d arid point. M, Figs. 3 and 4, and discharges C6 through relay U which pulls up but relapses almost immediately and the condenser is recharged. The relay U thus operates intermittently to flash tube Vf. The interrupted current operates a buzzer B which transmits impulses over leads N, 60 and 61 to terminals 2 in boxes B<SP>1</SP>1 and B1 and to a sound emitter X to give an audible warning at the sub-station. Secrecy. When contact S1 is closed on lifting the handset, battery applied to terminal e in box B operates an electromagnet in a mechanism described in Specification 806,308.