Patent GB-1243498-A (GB)
Title: System for connecting interconnecting electrical instruments
IPC: G10H1/00
Filed: 1970-05-07
Abstract: 1,243,498. Teaching music. WURLITZER CO. 7 May, 1970 [26 May, 1969], No. 22151/70. Heading G5X. [Also in Divisions H3-H5] A group of pupils each have an electronic keyboard instrument, such as a piano, and hear themselves over earphones so that they may practise privately without the need of separate rooms, the pupils instruments being coupled to one another, and to a similar keyboard instrument manned by a teacher, by means of a cable having as many wires as there are pupils instruments so that these instruments may each be selectively connected to one such wire for use as a private wire, there being an additional wire in the cable to which pupils may be connected in common for the purpose of ensemble playing, the pupils and the teacher having microphones for the exchange of speech. One teacher may serve four groups of six pupils -and can connect to an individual pupil, to overhear his practise, or to speak and be spoken to, or to demonstrate by use of the teacher's instrument, by operating one of six sets of ganged switches to select the subscriber's position in his group and by operating one of four sets of ganged switches to select the subscriber's group. These switches operate in simple co-ordinate fashion to connect the teacher to the cable of the wanted group and to the wanted private wire in that group. Each pupil's instrument has a six position switch which selects on a semi-permanent basis that one of the cable wires which is to be the instrument's private wire. Each pupils instrument also has a three position switch so that the instrument may be operated to play without the use of earphones but with the use of loud-speakers, other pupils and the teacher having no connection to the instrument in this mode; or so that the instrument may be operated with the use of earphones and with a connection to the selected private wire of the cable to permit overhearing and speech with the teacher; or so that the instrument may be used with its audio output connected to the group's cable common wire for ensemble playing with other members of the group, the earphones being connected to the private wires of the ensemble players over which the combined audio signals of the ensemble are received after transistor amplification and distribution provided separately for each pupil group at the teacher's instrument. For ensemble playing over the common wire it is necessary for the teacher to have operated a three-position key for the group from a neutral centre position into an ensemble position to connect the ensemble amplifier and distributer. Operation of these keys to a "mix" position allows the. inputs of ensemble amplifiers to be commoned so that ensemble playing can be extended to include pupils from more than one group. The ensemble amplifiers and distributers are also used by the teacher who, by operating a general call key and one or more of the group switches, can address and demonstrate to one or more groups of pupils. The operator's keyboard instrument, has four jack sockets into which audio aids, such as tape recorders and metronomes, can be plugged for broadcasting to one or more groups of pupils. Four-position switches for each group select which one of the four possible audio aids is connected to the ensemble amplifier which is itself connected by suitable operation of the ensemble/mix switch to broadcast the material. The pupils instruments have the private wire selector switch and the mode of use switch on the fall board which also carries the instruments loud-speakers, treble and bass at corresponding ends of the keyboard. A draw-leaf is provided beneath the keyboard for use as a writing surface. A pigeon-hole is provided beneath the keyboard for storage of the headset, the plug and jack connection being such that it cannot be disconnected unless the front panel of the instrument is dismantled and consequently discourages theft. The teacher's instrument has its switches mounted on the fall board, the loud-speakers for the instrument being beneath the level of the keyboard where a pigeon-hole is also provided for storage of the headset.