These curious 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
Used in VERY OLD audio tone based remote control equipment...well before the days of PLL's such as the NE567 - no digital here, everything was analog based
Used for both tone generation or as part of an audio tone filter
Iwata Japan
Tuning Fork Resonators - also referred to as "Microforks"
USED PULLS but absolutely working - removed from working equipment
Various frequencies (listed below)
Never seen one of these? They were used to filter or generate audio signals, I have associated devices such as the Murata D1200 and D1055 to make a complete system.
These microforks were considered "hi tech" in their day as prior to these, discrete LC tuned circuits were used for these audio frequency functions.
They have three terminals, input, common and output, physically very small - they appear very similar to crystal filters but these microforks are for much lower audio frequencies than quartz crystal based systems 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:
1597.5Hz (2)
1297.5Hz (2)
1383.0Hz
1177.5Hz
1057.5Hz
997.5Hz (5)
922.5Hz
877.5Hz
817.5Hz (2)
117.5Hz
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.
