Abstract: A method and related apparatus are provided for detecting the presence of a call waiting signal on a telephone line, where the call waiting signal is embedded in various signals. The call waiting signal frequency is isolated from the various other frequencies. The isolated call waiting frequency is then biased so that only the positive voltage portions of the signal are allowed to pass. Each positive voltage pulse as well as the zero voltage pulses are then sampled to determine whether they are representative of a biased call waiting signal. Each time a determination is made, one is added to a count on an up-down counter. When the count reaches a predetermined number, a call waiting signal is detected on the telephone line. Preferably an alarm signals the presence of a detected call waiting signal to the user. A disconnect switch interrupts a modem so that a person using the modem on the same telephone line will have sufficient time to answer a detected incoming call.

Abstract: A control device for programing information recorded upon a receiving part by an electrochemical marking head. In the main embodiment of the invention, the number recorded by the marking head is automatically sequenced after each marking cycle is completed.

Abstract: A marking head for use in the electrochemical process wherein a conductive metal part is imaged by firing electrodes against the part in the presence of an electrolyte. The marking face of the head contains an imaging board that includes seven segment digit modules that are capable of being fired in a pre-programmed order whereupon the characters recorded upon the part can be sequenced in a desired order. The segments are printed upon a copper coated board using a photoetching technique which leaves behind a copper coating in the segmented areas. Each segment is then coated with a carbon based material to provide a series of electrodes that can be efficiently operated in the presence of an electrolyte without breaking down.

Abstract: A system for injecting foam insulation into a wall cavity or the like that includes a flow control section having a detecting means for automatically inhibiting the control section when the gun is placed in an inoperative or off condition.