βML8204

The βML8204 is a tone ringer integrated circuit for telephone bell replacement, made by IPRS Băneasa [1].

The I.P.R.S. Băneasa Full Line Condensed Catalog (1990) lists the βML8204 and βML8205 as monolithic integrated circuits designed for telephone bell replacement; each has two oscillators, an output amplifier and a power supply control circuit, and the oscillator frequencies can be set over a wide range with the external components [1]. One oscillator, normally at a low frequency (fL), makes the second one alternate between its nominal frequency (fH1) and a higher frequency (fH2), giving a distinctive „warbling” tone; the output amplifier can drive a transformer or series-capacitor coupled loudspeaker, or a piezoceramic transducer, and the device can be powered from the telephone line or from a fixed DC supply [1]. The power supply control circuit has a built-in hysteresis that prevents false triggering and rotary dial „chirps”; the βML8204 can be triggered externally under logic control, and the βML8205 allows the adjustment of the power supply initiation current [1].

The catalog gives an operating temperature of −25…+70 °C (storage −25…+125 °C), a supply voltage of at most 30 V, a supply initiation voltage of 17…21 V, a sustaining voltage of 9.7…12 V, a sustaining current of at least 0.7 mA, a supply initiation current of 1.4…4.2 mA, a trigger voltage of at least 10.5 V and a disable voltage of at most 0.8 V (βML8204 only) and an output voltage (no load) of (V+) − 2 … V+ [1]. Pins (MP-48, top view): 1 V+, 2 trigger-in (βML8204; to be connected through a current limiting resistor when used) or initiation current (βML8205; to be connected to GND through an initiation current adjustment resistor), 3 RL, CL, 4 RL, 5 GND, 6 RH, 7 RH, CH, 8 tone output; pins 3 and 4 adjust the low frequency time constant, pins 6 and 7 the high frequency one [1]. The typical application (a βML8204 powered from the line through a bridge rectifier) is in the Gallery [1].