An arrangement for indicating the operational status of switches, particularly for use in electronic musical instruments, comprising:
- (a) a plurality of groups of switches, said switches being individually operable between ON and OFF states to cause the performance of selected functions;
- (b) an indicator connected with each of said switches and designed to indicate the operational state of the respective switch;
- (c) a plurality of devices each having a first input, a clocking input, and a series of stages designed to receive signals in a predetermined sequence via the first input in response to the delivery of clocking pulses to the clocking input, each of said devices being associated with a different one of said groups, and each of said stages having a first output which is connected with a respective switch of the corresponding group and with the indicator for the switch;
- (d) a control unit having a control input, and a clocking input common to and connected with all of said clocking inputs of said devices, said control unit comprising at least one memory having a plurality of sets of storage elements, and each of said sets being associated with a different one of said devices, each of said storage elements being associated with a different stage of the corresponding device, and said control unit having a plurality of second outputs each of which is connected with the first input of a different one of said devices and is designed to be sequentially connected with the storage elements of the corresponding set, said control unit further having a plurality of second inputs each of which is associated with a different one of said devices and is designed to be sequentially connected with the storage elements of the corresponding set, and said control unit being designed to generate a first series of clocking pulses subsequent to arrival of a control signal at said control input to thereby cause a reference signal to be advanced from one stage of each of said devices to another in the respective predetermined sequence, said reference signals resulting in the generation of identifying signals representative of the operational states of said switches, and each of said second inputs being connected with the storage elements of the associated set in substantial synchronism with the arrival of the reference signal at the corresponding stages to thereby permit information representative of said identifying signals to be stored in the respective storage elements, said control unit also being designed to generate a second series of clocking pulses subsequent to said first series, and said second outputs being connected with the storage elements of the associated sets in the respective predetermined sequence and in substantial synchronism with said clocking pulses of said second series so as to permit operating signals representative of said identifying signals to be furnished to the respective stages of said devices, each of said indicators providing an indication of the operational state of the associated switch in dependence upon the respective operating signal;
- (e) a plurality of signal generating circuits each of which is associated with a different one of said groups and has a first conductor common to and connecting all switches of the group to the corresponding second input of said control unit, each of said circuits being designed to generate series of identifying signals in the respective predetermined sequence during said first series of clocking pulses and to transmit the series of identifying signals to the corresponding second input in the predetermined sequence, and each of said circuits also being designed to generate a control signal upon changing of at least one switch of the respective group to one of its states;
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- (f) a second conductor for transmitting control signals to said control input, said second conductor being common to all of said switches and connecting all of said circuits with said control input.