The frontend_type can be any class in the /lib/Varien/Data/Form/Element/ directory. Whenever going to create a new field or group from admin system configuration section we should declared frontend type what we are going to declare.
• Button
• Checkboxes
• Checkbox
• Date
• File
• Hidden
• Imagefile
• Image
• Label
• Link
• Multiline
• Multiselect
• Note
• Obscure
• Password
• Radio
• Radios
• Reset
• Select
• Submit
• Textarea
• Text
• Time

———————————————————————————————————————————————————–

Corner of Blog:

“Save Tigers”

———————————————————————————————————————————————————–