What was APC mode on 8 track players?
I mean AFC
- Tony BLv 41 month ago
Spacemissing has answered in more detail that I could and is correct. I wonder why the thumbs down?
- spacemissingLv 71 month ago
Automatic Program Change.
A short piece of foil at the splice in the loop
makes contact with two insulated pieces of metal,
triggering the solenoid to move the head.
A few players and recorders had switches that would either allow (normal / APC)
or prohibit triggering the solenoid,
which permitted continuously repeating one program.
In most instances, AFC means Automatic Frequency Control,
which has nothing to do with tape.
It is found in FM tuners.
Before PLL (phase locked loop) tuners came into being,
many FM circuits would drift off frequency to the extent that
the listener occasionally had to re-fine-tune the station.
AFC pretty well cured that problem, but in early tuners with this feature,
the station had to be precisely tuned-in before the AFC was switched on.
Later, improved circuit designs allowed leaving the AFC on all the time;
it would work well enough that you could just get close to the right frequency
and the circuit would "pull" the tuner's oscillator to make up for any inaccuracy.
Another feature that IS associated with tape is ALC --- automatic level control.
This is almost always a crude compression circuit, making soft sounds loud
and limiting loud sounds to levels that would not saturate the tape.
Few tape aficionados would ever use ALC because
while it is sometimes tolerable for speech,
it produces very unpleasant effects when music is recorded.
Of course, in most portable recorders, the ALC is always on;
no switch is provided to defeat it.
There have been a few really effective ALC designs, though,
that can hardly be detected on speech
and don't make a total mess out of music.
Still, manual level control is preferable for any recording
if there is an adequate level indicator (meter) in the unit.