Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Aircraft; Human Factors
Aircraft ended up approx 900 feet low during descent.   Controller asked what altitude we were at when we realized we were too low.  Contributing factors:  1; This aircraft is the only one in the fleet without altitude capture.  2; there was no aural warning from the altitude alerter (we figured out after the fact that the volume on it was set to '1'; which was no sound.  3; crew was busy briefing the approach to the destination airport; and missed descending through the altitude.[Weather was] clear during the descent at time of event; but with overcast conditions below and at the destination airport.If the aircraft had an altitude capturing autopilot; this would not have happened.
Air carrier pilot reported receiving a low altitude alert from ATC during approach. Reporter cited limited autopilot capability as contributing.