Abstract: Visually and electronically readable temperature indicators have an electric circuit having a microchip and a bridge within the circuit and a porous substrate in direct contact with the bridge. The porous substrate has a first end protruding beyond a perimeter of the bridge with a temperature sensitive composition of a pre-selected melt temperature as a dry coating thereon. The bridge is formed of a conductive material and a binder. At a temperature at or above the pre-selected melt temperature, the temperature sensitive composition melts, migrates along the porous substrate to a position in contact with the bridge, thereby rendering the bridge electrically non-conductive or less conductive than an originally conductive state of the bridge, and provides a visible indication that the pre-selected melt temperature has been reached.

Abstract: A crawler device for pulling a leader string through electrical or cable conduit. The crawler device has a traction head, for example using caterpillar-type rubber tracks, biased outwardly into contact with the inner wall of the conduit when inserted in the conduit. The traction head pulls its own motor and power supply behind it, serially and flexibly linked to follow the traction head and negotiate curves in the typically small diameter electrical conduit. In the preferred from, the power supply is a series of linked batteries, such that the crawler is an independently and self-sufficiently mobile machine traveling through the conduit.