The term Tastschalter (German for momentary pushbutton switch) appears constantly in European IEC/DIN schematics, PLC manuals, and industrial control prints. Unlike a maintained switch, a Tastschalter only actuates while physical pressure is applied. Below is the definitive symbol reference mapping IEC 60617 to North American NEMA standards, complete with physical contact block pinouts.
The Complete Tastschalter (Pushbutton) Symbol Reference Table
Use this table to translate schematic symbols to physical hardware. The IEC pinout column refers to the standardized numbering stamped on modern contact blocks (like the Siemens 3SU1 or Schneider Harmony XB5 series).
| Function | German Term | IEC 60617 Symbol Description | NEMA Symbol Description | Standard IEC Pinout |
|---|---|---|---|---|
| Normally Open (NO) | Schließer (Taster) | Vertical line with a horizontal crossbar above, open gap. | Two parallel lines with a gap, bridged by a diagonal actuator line. | 13 and 14 |
| Normally Closed (NC) | Öffner (Taster) | Vertical line with a horizontal crossbar, closed gap (line passes through). | Two parallel lines touching, bridged by a diagonal actuator line. | 11 and 12 |
| Changeover (NO/NC) | Wechsler | Combined NO and NC symbols sharing a common actuator line. | Combined NO and NC symbols sharing a common diagonal actuator. | 11, 12, and 14 |
| Illuminated NO | Leuchttaster (Schließer) | Standard NO symbol with a small filled circle (light) adjacent. | Standard NO symbol with a circle and radiating lines. | 13 and 14 (+ LED pins) |
| E-Stop (Mushroom) | Not-Aus (Öffner) | NC symbol with a mushroom-head actuator line and positive-opening mark. | NC symbol with a mushroom head and manual reset indicator. | 11 and 12 (Forced open) |
Regional Variants: IEC 60617 vs. NEMA ICS 19
When reading international schematics, the visual language of the tastschalter symbol shifts depending on the governing standard. Understanding these regional variants prevents catastrophic wiring errors when retrofitting or repairing imported machinery.
The IEC 60617 Approach (Europe, Asia, Global)
The IEC standard relies on a minimalist, line-based syntax. The Tastschalter is represented by a vertical line (the conductor path) intersected by a horizontal bar (the contact). The actuator is a simple perpendicular line. The state of the switch (NO or NC) is determined by whether the horizontal bar bridges the vertical line (NC/Öffner) or sits adjacent to it with a gap (NO/Schließer). This standard heavily emphasizes the electrical state over the physical shape of the button.
The NEMA Approach (North America)
NEMA symbols, governed by standards like NEMA ICS 19, are more pictorial. A pushbutton is drawn using two horizontal parallel lines representing the stationary contacts, with a diagonal or vertical line representing the movable bridge. While NEMA is standard in US industrial panels, the global dominance of PLCs programmed in Europe (like Siemens S7/TIA Portal) means US technicians frequently encounter IEC Tastschalter symbols in HMI and ladder logic documentation.
Rows People Get Wrong (And How to Read Faded Schematics)
Even experienced bench technicians misinterpret specific rows in pushbutton reference tables. Here are the most common failure points and how to resolve them when the physical hardware markings are worn.
Mistake 1: Confusing Momentary (Tastschalter) with Maintained (Rastschalter)
A Tastschalter (momentary) returns to its resting state when released. A Rastschalter (maintained/latching) stays in its actuated state. In IEC schematics, a maintained switch is indicated by a small mechanical latch symbol (often a tiny hook or a cross 'X' over the actuator line) or a rotary switch symbol. Wiring a standard momentary pushblock into a circuit designed for a maintained switch will cause the machine to jog rather than run continuously.
Mistake 2: Ignoring the IEC Contact Numbering System
When a schematic is faded or the tastschalter symbol is ambiguous, trust the numbers stamped on the physical contact block. IEC uses a strict two-digit numbering convention for control contacts:
- 11 and 12: First Normally Closed (NC / Öffner) contact pair.
- 13 and 14: First Normally Open (NO / Schließer) contact pair.
- 21 and 22: Second NC contact pair.
- 23 and 24: Second NO contact pair.
If you are replacing a burnt-out Schneider ZB2BE101 contact block and the schematic just shows a generic pushbutton symbol, look at the stamped numbers. If the wires land on 13 and 14, you must order an NO replacement, regardless of what the faded ink on the schematic implies.
Mistake 3: The E-Stop (Not-Aus) Positive Opening Requirement
A standard NC Tastschalter relies on spring pressure to open the circuit. An E-Stop (Not-Aus) uses a positive opening (forced open) mechanism, where the physical actuator mechanically pulls the contacts apart even if they are welded shut by an arc. The IEC symbol for this includes a specific bracket or line breaking through the contact. Never substitute a standard 11/12 NC block for an E-Stop circuit; it violates safety standards like ISO 13850 and risks fatal machinery failure.
Frequently Asked Questions
What is the difference between a Tastschalter and a Rastschalter symbol?
A Tastschalter (momentary pushbutton) symbol shows a standard actuator line that springs back. A Rastschalter (maintained/latching switch) symbol includes a mechanical retention indicator—usually a small hook, a cross, or a rotary arrow next to the actuator line. In practice, a Tastschalter is used for 'Start', 'Jog', or 'Reset' functions, while a Rastschalter is used for 'Main Power Control' or 'Mode Selection'.
How do I interpret a Tastschalter symbol with a diagonal line or arrow?
Modifiers on the actuator line change the physical hardware required. A diagonal line crossing the actuator usually indicates an illuminated pushbutton (Leuchttaster). A mushroom-shaped cap on the actuator line indicates an E-Stop or emergency palm-button. A small arrow pointing at the contact gap indicates a proximity or limit switch actuated by machine movement, not a manual pushbutton.
Which standard applies to my region for pushbutton symbols?
If you are in North America, local panels will predominantly use NEMA symbols, though modern OEM machinery often defaults to IEC. If you are in the EU, UK, Australia, or working with imported European PLCs (Siemens, Beckhoff, Festo), the IEC 60617 tastschalter symbol standard applies universally. When in doubt, refer to the schematic's title block, which legally dictates the governing standard (e.g., 'Symbols per IEC 60617' or 'per NEMA ICS 19'). For a deeper dive into standard differences, consult resources like the Electrical Engineering Portal's symbol comparison guides.
