function traces = rt_control_saved(dirname, filename_mask, frequency)
if nargin < 3
    disp('loades traces saved by rt_control module');
    disp('usage: rt_control_saved(''20050114_rt'', ''20050114_1.0*'', 10000)');
    traces = -1;
    return
end
files = dir([dirname '/' filename_mask]);
total_files = size(files,1);
trace_size = files(1).bytes/4;
traces.voltage_uV = zeros(trace_size,1);
time_step_ms = 1e3/frequency;
time_length_ms = time_step_ms * trace_size;
traces.time_ms = time_step_ms:time_step_ms:time_length_ms;
for file = 1:total_files
    filename = [dirname '/' files(file).name];
    disp(filename); 
    fid = fopen(filename);
    traces.voltage_uV(:,file) = fread(fid, [1,inf], 'int32');
    fclose(fid);
end
disp(sprintf('%d traces of %d ms loaded.',total_files,time_length_ms));