Multiple device control system

In a control system for trains having a plurality of cars, each having a continuous galvanically conductive trainline extending from car to car, a power supply circuit for supplying power to said train line, a car ground, a transmitting circuit, and a receiving circuit with each of said transmitting and receiving circuits connected to said trainline to receive power from the trainline, the combination comprising,

• a first means for activating a car to become a master car,
• means operative upon activation of a master car for connecting the power supply circuit of said master car to said trainline to supply power thereto and disconnecting all other power supply circuits from the trainline,
• means operative upon activation of a master car for connecting the car ground of said master car to said trainline and disconnecting all other car grounds from said trainline,
• and means isolating the non-master receiving and transmitting circuits from the grounds of their respective cars.

A control system for a plurality of separately located units to be controlled form any one of said units,

• said units being interconnected only by a single line formed of two continuous conductive wires,
• each unit comprising a voltage supply circuit adapted to supply voltage to said line, a transmitting circuit, and a receiving circuit, said voltage supply circuit being independent of said transmitting and receiving circuits,
• the transmitting circuit and receiving circuit of each unit being continuously connected across said two-wire line,
• means at each unit for causing its voltage supply circuit to be connected across said line and
• means operative upon connection of one voltage supply circuit to said line for causing the voltage supply circuit of all other units to be disconnected from said line, whereby said line is supplied from only one voltage supply circuit at any time.

A multicar train system comprising

• a continuous two-wire line extending serially from car to car along said train from one end of the train to the other,
• each car of the train having a transmitter and a receiver, each connected in parallel to the line,
• a direct voltage source coupled across said line at a selected car, said line having no other voltage or power sources connected to said line,
• means at each transmitter to apply a shunt to said line in correspondence with one bit of a binary digital signal to increase the current in said line and reduce the voltage across said line at all points along the line during such shunting, and
• means at each receiver for responding to said voltage reduction to detect said signal,
• said source including a regulator having a regulated voltage output mode for current output not exceeding the aggregate current drawn by all said transmitters and receivers in the absence of transmission of data along said line and having a regulated current output mode for current draw substantially greater than said first current output,
• said shunt-applying means being operative to provide a current draw from said regulator to cause said regulator to operate in its regulated-current mode.

A system comprising

• a transmitting circuit,
• a receiving circuit
• a two-wire line connecting said circuits,
• a single voltage source connected across said line for supply voltage to said line,
• means for transmitting binary information in the form of binary bits of two types from said transmitting circuit to said receiving circuit, comprising means at said transmitting circuit for applying a low impedance load across said line to reduce the voltage at said receiving circuit in correspondence with each occurrence of a bit of said binary information of one type,
• said voltage source having means maintaining both a substantially uniform voltage for loads having a range of impedances greater than said low impedance load and a substantially constant current for loads having a range of impedances substantially equal to or less than said low impedance,
• said receiving circuit including an input having a zener diode connected across said line, said diode having a regulating voltage at least as large as the voltage created at any receiver by the resistive volt-drop in said line between said transmitting and receiving circuits during marks of said binary information, said regulating voltage also being less than that of said voltage source, whereby said diode will conduct in the absence of application of said low impedance load to maintain said receiving circuit in a mark state.

A multicar train system comprising

• a continuous two-wire line extending serially from car to car along said train from one end of the train to the other,
• each car of the train having a transmitter and a receiver, each connected in parallel to the line,
• a direct voltage source coupled across said line at a selected (master) car, said line having no other voltage or power sources connected to said line,
• means at each transmitter to apply a shunt to said line in correspondence with one bit of a binary digital signal to increase the current in said line and reduce the voltage across said line at all points along the line during such shunting, and
• means at each receiver for responding to said voltage reduction to detect said signal,
• each car having a direct voltage source and said system also including means for coupling a second voltage source of a non-master car to said line, and for concurrently preventing all other sources except said second source and including said first source from being connected to said line, whereby the car having said second source becomes master car.