Clamp signals

A clamping signal consists of a number of segments, generated by the respective commands.

Each of the above signals can have parameters set as constants, for example:

<level>
        <expr> -86</expr>
        <expr> 50  </expr>
</level>
or as variables defined in signal or record files, for example:

<expr>level = -86</expr>
<expr>dur = 50</expr>

<level>
        <expr>level</expr>
        <expr> dur</expr>
</level>