Signal 3 software

Signal delivers powerful sweep-based data capture and analysis, stimulus generation and control using one of the CED 1401 family of data acquisition peripherals. Derived from the popular SIGAVG software, Signal is used in laboratories world-wide for a broad range of applications. Version 3 is the latest release of this versatile software package.

Signal records a combination of waveform data, external states and keyboard markers and can append a wide variety of auxiliary data to sampled sweeps. Sweeps can be un-triggered, post-triggered or peri-triggered. Stimuli can also be generated while sampling.

Analyses include waveform averaging, power spectra, amplitude histogram and measurements of areas, means, latencies, RMS amplitude and SD based on cursor positions or automatic feature detection. Specialised analyses are provided for whole-cell current clamp, voltage clamp and single channel patch clamp.

Signal's easy-to-use interactive interface provides all the data capture, data analysis and display control that many users require. Repetitive tasks, custom analyses and management of complex on-line experiments can be automated using the built-in script language.

Signal features

Fast sampling of multiple channels; maximum speed and number of channels dependent on 1401 type
On-line and off-line data analysis including waveform averaging (with error bars), power spectra and amplitude histograms
Automatic generation of multiple averages from one data file and grand averages across multiple files
Waveform feature detection and measurements both on-line and off-line to generate XY plots
Data export to other applications as text or picture; direct export of data to spreadsheets
Data import from a wide range of third-party files
Automation and customisation of analyses and repetitive tasks
Finite Impulse Response (FIR) filtering
Curve fitting using a variety of fit equations; fit coefficients can be plotted automatically
Multiple configurable views of the same data file, even during sampling
Output sequencer allows flexibility of output stimuli, reaction to sampled data and complex interaction with scripts
Tools for analysing whole-cell voltage clamp, current clamp and single channel patch clamp (idealised trace, open/closed time histograms)

Data acquisition

Record and display fast sweeps of waveform data to disk with over 15,000,000 data points per sweep with a base level Power1401
Output pulse, sine, ramp and stored waveforms while sampling
Generate sets of varying stimuli (pulses, ramps) on up to 8 DAC outputs while sampling, sequence through multiple sets of stimuli
Sample multiple waveform inputs at aggregate rates up to 625kHz
Switch sampling configurations and output protocols
Capture free-running or triggered sweeps with post or peri-trigger modes
Tag data frames to indicate external states and artefacts for selective review and analysis
Perform built-in and custom analyses on incoming sampled data
Configure dynamically programmable amplifiers including the CED 1902 low-noise amplifier and Power1401 gain option
Detect waveform features with active cursors, measurement to XY plot (I/V plot generation)
Sample at arbitrary or varying rates with external convert input option

Advanced features

Voltage and current clamp
Signal generates all of the stimuli needed for voltage and current clamp protocols, including pre-recorded action potential waveforms. Multiple sets of stimuli can be stored in one sampling configuration and selected manually or automatically sequenced. Voltage stimuli levels are either relative to an adjustable holding potential or fixed. Leak-subtraction and I/V plots are always available even while sampling. Curve fitting can be applied to raw data, leak subtracted data and I/V plots.

Single channel patch clamp
The open/closed menu item generates an idealised multi-level current trace from patch data. The idealised trace is editable by dragging open/closed times and amplitudes; there are additional tools for splitting and combining events. Amplitude histograms can be generated from the raw data or idealised traces. Dwell time histograms are generated from the resultant traces. Curve-fitting can be applied to the derived traces or histograms.

Complex stimuli and experimental control
Signal is capable of generating a vast range of output stimuli: up to 256 sets of up to 500 pulses. Pulses are fixed or they can change amplitude and duration on each repeat. Outputs can be altered or redefined while sampling continues.

There are two methods for generating outputs. The graphical sequence editor converts displayed pulses into the underlying output commands. This covers the majority of stimulus requirements in an easy to use drag and drop environment. If your requirements cannot be met with the graphical editor you can define your outputs with the underlying commands as a text sequence of instructions.

The script language has further experimental control options including communication through serial lines and commands for starting and stopping other programs.

Script language

Signal is a powerful interactive package with the turnkey functions needed by most users. It is further enhanced by the use of scripts. These range from instructions for simple analyses to highly complex experimental control. Scripts can customize sampling, on-line and off-line analysis, data manipulation, data display and saving of results.

CED script language features

High-level commands for performing complex analyses with a single instruction
Programmable toolbars, pop-up windows and dialog boxes for custom user interfaces
Familiar control structures (for/next loops, procedures, etc.)
Debugging tools including breakpoints, single-stepping and access to variable values
Script text editor with drop down function list, syntax colouring and split window options
Context sensitive help

Whilst many users write their own scripts, CED provides a script-writing service and continues to develop and maintain a library of scripts. These are available to customers and provide a wide range of tailor-made functions such as complex waveform analysis and averaging across multiple files.

To get you started writing scripts, the Signal package includes example scripts to use as templates, scripts that automatically generate code for toolbars and dialogs, a comprehensive script reference manual and a training manual with tutorials on a range of script writing topics. You can also write scripts by example! To do this, turn on script recording, do the actions to be recorded and turn off script recording. Signal will open a new window holding the script command equivalents of your actions.

Evoked response and TMS Fixed, random and pseudo random pulse outputs with on- and off-line waveform averages and latency detection. Auto-averaging enables the user to specify the last n frames to form an average and measurements can be taken automatically from the results.
Voltage or current clamp Control of holding potential and pulse outputs using the graphical sequencer. On- and off-line construction of I/V plots in XY views and leak subtraction.

Single channel patch clamp Automatic drawing of single and multi-level channel openings on- and off-line. Once the idealised trace has been produced, measurements such as open/closed time and amplitudes can be taken.

EMG Record single and multiple channels of EMG with software control of amplifiers such as the CED 1902. Perform rectification and smoothing at the touch of a button or automatically with a script. Produce power spectra that update as new data sweeps are recorded.

Cardiac action potential Use active cursors to locate the CAPs and then position cursors at other points, such as repolarisation percentages. Script interaction with the cursors can aid report generation.

Transients Detect waveforms rising or falling below a threshold as a trigger. Capture peri-trigger data up to the available size of memory inside your 1401. Optionally output stimuli in response to the trigger.

Auditory evoked potentials Generate complex stimulus protocols and reports under script control. Features include: automatic artefact rejection, digital filtering, generation of sub and grand averages and feature detection using active cursors.

Teaching Custom scripts run student practicals written to the exact specifications given by tutors. Features include the use of help files with experiment instructions and comparison of computer measured results with those of the student.

New version 3 features

Sampling

Direct access to the text sequencer underlying the graphical interface gives maximum flexibility and control of pulses and waveform output
Enhanced amplifier telegraph data support and usability
Optional trigger polarity inversion
External convert sampling input for arbitrary or varying sample rates

Analysis

Improved curve-fitting facility: fit to polynomial, exponential, sine and Gaussian functions on single or multiple frames
Patch clamp analysis generates idealised current traces
Analysis and editing of idealised traces
Idealised trace import from CED DOS Patch software
Improved amplitude histogram analysis
Enhanced auto-average measurements
Copy and paste traces to and from XY views
Matrix functions built into script language

Control

Multiple monitor support
Channel information dialogs
Cubic-spline drawing mode in result views
New window dialog for easy selection and clean-up
Overdrawn channels with optional locked Y axis and offset
Independent colours for channels

Signal version 3 requires one of the CED 1401 series of intelligent laboratory interfaces and a PC with Windows 95, 98, Me or Windows NT 4, 2000 or XP. We recommend that the PC has a minimum 256 MB of RAM.