Electromechanical Switch Terminology

Types of Switches

BREAK-BEFORE-MAKE: Disconnecting the RF power from the current RF circuit position before selecting a different position. All CHARTER ENGINEERING switches are break-before-make designs.

SPDT SWITCH: A single-pole, double-throw switch has one input port and two selectable output ports.

SPDT TERMINATED SWITCH: A single-pole,double-throw switch with one open output RF port internally terminated in a 50-ohm resistive load.

MULTI-POSITION SWITCH: A switch with one input and more than two outputs. Standard CEI multi-throw switches provide up to 12 (tweleve) selectable outputs from a single input.

MULTI-POSITION TERMINATED SWITCH: A multi-position switch with each unused or open output RF port internally terminated in a 50-Ohm resistive load.

TRANSFER SWITCH (DPDT): A transfer switch has two independent paths that operate simultaneously in either of two selected positions. These pairs are actuated simultaneously. This actuation is similar to that of a double-pole double-throw switch.

Actuator Terminology

FAILSAFE: A mode of operation in which the switch moves to the closed position when the actuating voltage is applied and always returns to a predetermined position when the voltage is removed.

LATCHING: Also called pulse latching, a mode of operation in which the switch remains in a preselected position whenever the actuating voltage is removed or interrupted, and holds that preselected position until a voltage is applied to another position. In order to change to another position the voltage must then be reapplied to the position desired. The latching models can also operate by pulse voltage at a 30 millisecond pulse minimum. The pulse voltage technique can save power and will allow the system to run at cooler temperatures.

MOMENTARY (NORMALLY OPEN): A mode of operation in which all output ports of the switch are disconnected from the input port until a voltage is applied to maintain a selected position. The switch returns to its open position with the removal of voltage.

Electromechanical Switch Options

INDICATOR CIRCUITRY: A set of internally mounted contacts mechanically connected to the switch actuator allowing external monitoring of switch RF status.

SUPPRESSION DIODES: This option offers fast-recovery rectifiers (diodes) connected in parallel with the coics of the switch to suppress any transient voltage generated by the coils. Suppression Diodes are recommended with TTL Logic.

COMMAND INPUT COMMAND VOLTAGE (POLARITY): A mode of operation is which the supply voltage and control voltage can be positive or the return voltage be negative (this catalog designates the “+” or positive and the “-” or negative signs). To select a position using positive voltage the common voltage must be the return voltage. To select a position using return voltage the positive must be supplied at the common terminal.

TTL LOGIC: Transistor-transistor-logic driver circuitry which enables the status of the switch to be controlled by the level of the TTL logic input.

BCD TTL DECODER: Completely contained within the switch housing, BDC logic circuitry establishes compatibility of the switch with binary login inputs.

This applies to a latching type switch only. A switch that has the ability to disconnect the actuator drive circuit so that D.C. current will not be consumed after switching has been accomplished.

LOW, ULTRA LOW, OR SUPERIOR PASSIVE INTERMODULATION (PIM): This option allows for a -110 dBc (LOW), 130 dBc (ULTRA LOW) or -160 dBc (SUPERIOR) passive intermodulation (PIM) level @ the PIM frequency. PIM is a form of signal distortion that occurs whenever signals at two or more frequencies conduct simultaneously in a passive device which contains some non-linear response.