Rated Load:

The load which the contacts can reliably switch in a regulated load.

Contact Form:

The arrangement of the contacts in the relay. This determines how many circuits the relay can operate.

Form 1A (or “1 Form A): One circuit being opened and closed with the contacts in a Normally Open position.

Form 1B (or “1 Form B): One circuit being opened and closed with the contacts in a Normally Closed position.

Form 1C (or “1 Form C): One circuit being transferred to another circuit. This requires three terminals, one input with two outputs. The one input can be switched between the two outputs. Example; This can be used to transfer power from a line voltage to a battery backup.

Form 1X (or “1 Form X): Two circuits, one Form 1A and one Form 1B. When the relay operates it closes the Form 1A contact and opens the Form 1B contact. This requires two inputs (one normally open, one normally closed) and two outputs.

Form 2A (or “2 Form A): Two circuits being opened and closed with the contacts in a Normally Open position.

Form 2B (or “2 Form B): Two circuits being opened and closed with the contacts in a Normally Closed position.

Form 2C (or “1 Form C): Two circuits being transferred to another circuit. This requires six terminals, two inputs with four outputs. The two inputs can be switched between the four outputs. Example; This can be used to transfer power from a line voltage to a battery backup.

Form 2X (or “2 Form X): Two circuits, one Form 2A and one Form 2B. When the relay operates it closes the Form 2A contact and opens the Form 2B contact. This requires four inputs (two normally open, two normally closed) and four outputs.

Form 3A (or “3 Form A): Three circuits being opened and closed with the contacts in a Normally Open position.

Form 3B (or “3 Form B): Three circuits being opened and closed with the contacts in a Normally Closed position.

Normally Open (or “NO”): Refers to contacts which are in the Open Position when the relay is not energized.

Normally Closed (or “NC”): Refers to contacts which are in the Closed Position when the relay is not energized.

SPST: Single Pole Single Throw. Refers to a relay that operates one circuit. Can be either Form 1A or Form 1B depending on if the contacts are either Normally Open or Normally Closed. These relays are usually then referred to as “SPST-NO” or “SPST-NC.”

SPDT: Single Pole Double Throw, same as Form 1C.

DPST: Double Pole Single Throw. Refers to a relay that operates two circuits. Can be either Form 2A or Form 2B depending on if the contacts are either Normally Open or Normally closed. These are usually then referred to as “DPST-NO” or “DPST-NC.”

DPDT: Double Pole Double Throw, same as Form 2C.

3PST: 3 Pole Single Throw. Refers to a relay that operates three circuits. Can be either Form 3A or Form 3B depending on if the contacts are either Normally Open or Normally closed. These are usually then referred to as “3PST-NO” or “3PST-NC.”

Contact Material:

AgSnO­2­: Silver Tin Oxide, low welding tendency, high wear resistivity with heavy loads, low material transfer. Used in circuits with high requirements to makes and/or breaks currents, DC and AC loads, recommended range of application ≥ 12V, 10mA.

Max Switching Voltage:

The maximum voltage between the contact members before closing or after opening of a relay contact. The switching power is usually specified in Watts for DC and VA for AC.

Max Switching Current:

The maximum current which a relay contact makes and/or breaks

Max Switching Power:

The maximum power which a relay contact makes and/or breaks.

AC power: power generated by an alternating current
DC power: power generated by a direct current

Electrical Endurance:

Number of cycles without contact failure under full load, under specified conditions. One cycle consists of opening AND closing the relay once

Mechanical Endurance:

Number of cycles without changing state under no load, under specified conditions. One cycle consists of opening AND closing the relay once.