Patent GB-1294305-A (GB)
Title: Improvements in or relating to a station for connection to a telephone system
IPC: H04M1/56
Filed: 1969-10-24
Abstract: 1294305 Substation equipment; iriterconnection systems; two-way transmission; impulse transmitters S Z M GABR 24 Oct 1969 61989/68 Headings H4J H4K and H4R A loud-speaking telephone substation has switching means which can be selectively set to connect an incoming call to the loud-speaker either automatically or under manual control, and diaphragm means of the microphone means is positioned directly in front of the loud-speaker and so as to receive equal (cancelling) signals from the loud-speaker. Fig. 1 shows one substation connected to an exchange line at 22 and connected to an interconnection system (Fig. 7) including a plurality of other stations (each provided with a microphone 42, reproduction unit 44, amplifier 46 and switching circuit 48) and a closed circuit television system comprising a camera 54, a monitor or receiver 58 and a switching circuit 56. Electro-plotters and electro-writers could be included. The substation comprises a handset 10, a microphone 12 and amplifier 14, a loud-speaker 16 and amplifier 18, a line transformer 22, dial and speech circuits 30, 26 and 28, a switch unit 24, a ringing detector 20, and end of call detector 32, a switch and indicator unit 34, a switch-off indicator unit 26 and a tape recorder 38 which can be used to record telephone conversations or can act as an automatic answering machine. The loud-speaker amplifier includes an A.G.C. circuit to prevent singing and the microphone amplifier includes an A.G.C. circuit to bring signals picked up by the microphone to a set level. The substation transducers may also be orientated and controlled as in Specification 1,270,431 to further prevent acoustic feedback. The circuits 10, 26, 28 and 30 may be replaced by a conventional handset to which the microphone and loud-speaker amplifiers are coupled inductively. The substation may also include a transistor amplifier the gain of which is controlled by the subscriber. The substation which is also said to be used as part of a public address system has three modes of operation selected by switches on unit 34. In one mode, the detector 20 responds to an incoming call, after a predetermined number of rings set by the subscriber, and connects up the loud-speaker and microphone. At the end of the call, detector 32 responds, after a delay set by the subscriber, to absence of speech, or tone signals from the calling subscriber to terminate the connection. An outgoing call is initiated by operation of a switch on the unit 34. In another mode, a switch on unit 34 must be operated for calls in either direction. In either of these modes lifting of the handset automatically cuts out the loud-speaker and microphone. In the third mode the handset is connected for conventional working. Figs. 2 to 5 (not shown), show various ways in which the microphone and its amplifier can be connected to the telephone line. Fig. 6 (not shown) shows connections for the loud-speaker instrument and its amplifier. The telephone instrument at the substation may have illuminated push-buttons arranged in a circle or circles concentric with a dial which may have the microphone at its centre. The push-buttons are for tone signalling, e.g. to indicate the class of service. The instrument also carries indicators which indicate the digits of the last number dialled. This number may also be indicated at the supervision point, and a printed record may be made. The substation may also have paging facilities in the form of electronic indicator tubes or a pointer rotating relative to a scale, driven by coded pulses of a frequency outside the audio range to indicate at the substation the particular person with whom communication is required. Additional loud-speakers or a multi-coil loudspeaker may be used for the additional signals. Automatic dialling.-A directory pad comprises a stack of superimposed leaves having stepped edges and pivoted together along one edge. A lid is positioned as a top leaf for the stack. The lid carries a knob which slides across the lid moving two arms so as to engage stepped edge portions of the leaves. With the knob in a selected position engaging a particular leaf the lid is opened to select the leaf. A corresponding bank of storage cells are, selected. The subscriber then selects a particular subscriber mentioned on that leaf and presses a corresponding button. Depression of the button selects a particular cell in the storage bank. A cell may comprise a set of wheels or discs, one per digit, each having a movable contact set to engage a fixed contact corresponding to the digit stored and adapted to control an impulsing mechanism. Each wheel or disc can be set to store a different number by repeatedly pressing button which advances the wheel or disc one step.