Electrically conductive materials

An electrically conductive resistance heating system, comprising:

• a carbonised fabric heating element having a characteristic that as the temperature of said carbonised fabric heating element increases, the resistance of said carbonised fabric element decreases;
• means for applying a potential difference across said carbonised fabric heating element, and an electrical control circuit arranged to control the temperature of said carbonised fabric heating element, and to derive a control signal from an electrical current passing through said carbonised fabric heating element, said electrical control circuit further comprising comparative switching means first and second inputs and acting to selectively apply and remove said potential difference across said carbonised fabric heating element;
• wherein said electrical control circuit further comprises:
• thermostat means having an output, said comparator switching means receiving at the first input the output of said thermostat means and at a second input either the control signal when the potential difference is being applied across said carbonised fabric heating element or the output of a gradual decay circuit when the potential difference is not applied, said gradual decay circuit output being initially representative of said control signal but gradually decaying;
• the operation of said comparator switch means being to apply the potential difference across said carbonised fabric heating element only when the first input signal is greater than the second input signal.