Abstract: A safety valve for exposing a measuring probe to a fluid comprising a hollow inner valve body with a valve seat movably positioned within a hollow outer valve body having a cooperating valve element for providing fluid-tight engagement when the valve is closed. The inner valve body partially extends from the outer valve body when the valve is open for passage of the fluid into an inner chamber for exposing the inserted probe to the fluid. The probe is secured to the inner valve body by a threaded cap, the movement of which is translated to the inner valve body in the presence of the probe for moving the inner valve body to the open valve position. The valve is prevented from being opened in the absence of the probe by a spring mounted on the outer valve body engaging a catch on the cap for restricting movement thereof preventing the valve from being opened.

Abstract: An alarm system, particularly for use on a train, responsive to a plurality of different alarm conditions for providing outputs for indicating which one or ones of the alarm conditions have been detected. A signal having at least as many frequency components as there are alarm conditions is generated on a transmission line which runs the length of the area over which the conditions are to be detected. Alarm sensing switches are connected to taps of the transmission line, and each switch is connected to a frequency dependent impedance means which is resonant and has a low impedance at one of the frequencies. A filter is provided for each alarm condition to be detected, each such filter having a band pass at one of said resonant frequencies. The presence of an alarm condition causes an alarm switch to change state, which causes one of the impedance means to short circuit a frequency which otherwise would have been passed by one of the filters, thus indicating the presence of an alarm condition.

Abstract: Apparatus for preventing damage to resistor grids in the propulsion controller circuit of a direct current motor, particularly of the type used in driving railway vehicles, in which a line breaker relay is de-energized whenever the propulsion controller fails to progress from the switch position to the full series position within 15-25 seconds. The line breaker relay remains de-energized for the duration of the power cycle of the propulsion controller and becomes operational automatically after the master control handle is returned to the off position.

Abstract: A system and method for providing entertainment and/or information to vehicles travelling along a roadway. The system of the invention enables the driver to tune his car radio to a single station while travelling on a specific long-distance road, and to receive high quality and continuous radio reception for the duration of his trip on the road. An antenna comprised of at least one conductor is strung adjacent to the roadway and parallel thereto, and is excited with an amplitude modulated radio frequency signal within 550 to 1650 khz broadcast band so that each vertical slice through the antenna is effective as an electrical multipole. The antenna excitation signal is arranged to be large enough so that the vehicles on the roadway, which are substantially within the near field of the antenna, receive substantial and usable radio signals, but small enough so that radiation at distances beyond the roadway is negligible, so as not to interfere with broadcast reception beyond the highway.

Abstract: Apparatus for preventing overvoltage and overcurrent damage to direct current motors, and wheel lockout in electrically powered vehicles having dynamic and mechanical brake assemblies includes dynamic braking voltage and current sensing circuits, a first network responsive to detected dynamic braking voltages exceeding a predetermined value, a second network responsive to dynamic braking currents exceeding a predetermined level, and a third network responsive to dynamic braking current exceeding a different predetermined level at the same time that excessive mechanical braking occurs and for providing an output when such conditions coexist for more than a predetermined time period, and an interrupting circuit responsive to outputs from the first, second, and third networks for interrupting dynamic braking and substituting therefor mechanical braking.

Abstract: An entertainment and public address system especially suited for mass transit vehicles, including a tape recorder on which is recorded information such as music, news bulletins, announcements, and the like, connected through appropriate amplification circuits to speakers for playback within the listening range of the vehicle passengers. A separate public address circuit is provided for the vehicle operator or conductor and includes a switch which, when actuated, connects a microphone of the public address system through the amplification and speaker network and also energizes a time delay network to rewind the tape recorder a preselected amount regardless of the length of time the public address system is in use. Release of the switch returns the system to normal operation whereupon the rewound tape recorder plays back the last portion of the interrupted recording so as to: preserve continuity of the information being perceived by the passengers.