These devices date back the 1970's when remote control of devices and equipment was commonly performed by sending audio frequency tones, usually via a radio communications link.
These devices were used for everything from remote controlled garage doors, pagers, security access systems etc
No digital here, everything is analog based
Murata Japan
Tuning Fork Resonators - these are also referred to as "Microforks"
USED PULLS but absolutely working - removed from working equipment
Various frequencies (listed below)
Never seen one of these? They are used to filter or generate audio signals, I have associated devices such as the Murata D1200 and D1055 to make a complete system.
They have three terminals, input, common and output, physically very small - although they appear very similar to crystal filters, these are designed for much lower audio frequencies and use a piezo element
Bandwidth is 2 ~ 5 Hz
They are used as band-pass filter or resonator in high stability audio oscillators
Frequencies available:
2500.0Hz
1700.0Hz
967,5Hz
879.0Hz (2)
877.5Hz
832.5Hz
802.5Hz
Very interesting devices to experiment with - I can supply a very detail 22 page applications book (pdf format) - one of the photographs shows a very simple and yet extremely accurate audio oscillator built around these devices.