The present invention relates to signal generators and more particularly to extending the addressing capability of a minicomputer to allow real time control of a wide range and large number of peripheral devices to produce a large range of signals. 
A particular use for the apparatus is in the field of Nuclear Magnetic Resonance (N.M.R.) imaging where a large number of (R.F.) pulses and adjustments at varying time intervals may be required to provide for the preparation of an N.M.R. image.  The apparatus is known for simplicity as CONBUS and will be so referred to hereinafter.  CONBUS is defined for the purpose of the present invention as a control apparatus connectable between a digital computer and a large number of peripheral devices to enable the control of such devices by the program stored in the digital computer. 
In N.M.R. imaging a minimal number of computer Input/Output (I/O) instructions are required to alter variables such as R.F. pulse length, spacing, power and sequence length and format; gradient position strength and allocation.  The R.F. pulses are fed for example to a coil such as described in co-pending application Ser.  No.  337,184.  Sequences which electronically vary the contrast in N.M.R. images can be constructed simply by a small number of instructions.  Also through its control of magnetic field gradients CONBUS allows an operator to steer a gradient through any position in space thereby allowing images to be formed from any plane in any direction as described in the above co-pending application. 
According to the present invention there is provided a signal generator for generating signals to control a large number of peripheral devices, including a digital computer having N device select lines, M output control lines and P data output lines, in which one of the N device select lines is used to enable CONBUS (as hereinbefore defined) and in which following enabling of CONBUS the P data output lines and M output control lines are used to select and to control each of the large number of peripheral devices. 
The invention also provides a method of generating signals to control a large number of peripheral devices using a digital computer, in which during a first stage the area within which a selected device is present is chosen using a first control output from the computer and one or more data outputs, in which during a second stage the device within the area is selected using a second control output and one or more data outputs, and in which control data for adjusting the device is supplied during a third stage using a third control output and one or more data outputs.