Casella CEL CEL-278 - Manual (Page 15)

When the button is pressed while standing in the highest frequency filter
band, the instrument returns to the 'All Pass" band. Conversely it returns to
the highest band when the
button is pressed while standing in "All Pass".
3.4 Input Facilities
The CEL-278/2 accepts analog noise signals from the Sound Level Meter for
frequency analysis. It will also accept control signals from an external device
to step the filters.
Figures 4 and 5 show the line connections for the top and bottom connectors.
The analog input conditions are as follows.
1.
Conditioned AC signals up to 8.0V RMS, 11.3Vpk with a maximum of
1 kΩ source impedance, input via line 4 of the top connector.
The remote control facilities are as follows.
1.
Filter step up: raise line 3 to + 5V with respect to line 2 for a minimum
of 25ms, then open again to step filter to adjacent higher frequency
band.
2.
All stop reset: dose line 6 to line 2 for a minimum of 25ms, then open
again to reset scan to "All Pass" band for start of a remote controlled
frequency scan.
3.5 Output Facilities
The CEL-278/2 delivers filtered analog noise signals to the Sound Level
Meter for level measurement. Figures 4 and 5 show the line connections for
the top and bottom connectors.
The output conditions are as follows.
CEL Instruments Ltd. CEL-278/2 Handbook Page 15