What is BS EN 61240 - Outline drawings of SMD for piezoelectric devices about?  
BS EN 61240 is an international standard that discusses piezoelectric devices for the preparation of outline drawings of surface-mounted devices (SMD) for frequency control and selection.
This International Standard sets out general rules for drawing all dimensional and geometrical characteristics of a surface-mounted piezoelectric device package (referred to in this document as SMD) in order to ensure mechanical inter-changeability of all outline drawings of the SMDs for frequency control and selection.
Who is BS EN 61240 - Outline drawings of SMD for piezoelectric devices for? 
BS EN 61240 on the preparation of outline drawings of SMD is useful for: 
- Manufacturer of piezoelectric devices
- Manufacturer of consumer electronic devices 
- Product design engineers
- Entities involved in technical and engineering drawings
- Technical consultants
- Mechanical engineers
Why should you use BS EN 61240 - Outline drawings of SMD for piezoelectric devices?  
A device outline drawing is a drawing that includes all dimensional characteristics required for the mechanical interchangeability of the complete device. The device outline drawing includes the case or body, all terminals, and the locating tab if present. Regarding the current situation of many quartz crystal device suppliers, many of them use their own enclosure layouts in their catalogs. For the convenience of consumers, general rules of enclosure layout and definition of size need to be unified.
BS EN 61240 provides guidance on the title of the outline drawing, composition of the outline drawing, and requirements for terminal leads.
The international standardization represented by these drawings, therefore, encourages manufacturers of devices to comply with the tolerances on the drawings in order to extend their range of customers internationally.
What’s changed since the last update?
BS EN 61240:2017 supersedes BS EN 61240:2012, which is withdrawn. BS EN 61240:2017 includes some technical changes with respect to BS EN 61240:2012. These include: 
- Outline drawings have been changed from three views (top, front, and bottom) to that based on ISO layout in the third-angle projection, in which the view from the right has been added to the top, front, and bottom views
- Reference line and geometrical dimensions of the package for enclosures have been changed for practical use
- Information on miniaturized leadless ceramic enclosures of piezoelectric devices (SMD) for frequency control and selection has been included in an annex 
