1231-P5
The General Radio 1231-P5 Adjustable Filter was introduced in Catalog M (1951) and remained available through Catalog P (1959).
The Type 1231-P5 is designed as an accessory filter for the Type 1231-B Amplifier and Null Detector. Its purpose is to increase selectivity, reduce noise and harmonics.
The internal filters are parallel-resonant circuits, consisting of toroidal inductors and fixed capacitors for the 11 frequencies. Four additional switch positions are provided for selecting toroid inductors L1 thru L4 only. A pair of terminals for an external capacitor can be used for tuning the filter to any frequency from 20 Hz to 100 kHz.
CAUTION: The Type 1231-P5 filter should not be subjected to any DC current.
Specifications
- Filter Frequencies: 11 settings; 50, 100, 200, 500 Hz; 1, 2, 5, 10, 20, 50, 100 kHz
- Frequency Calibration: Within ±2%
- Selectivity: Better than 30 dB against the second harmonic
