Rainbow Electronics ISD1800 - Manual (Page 11)

ISD1800 SERIES
Publication Release Date: June 7, 2005
- 11 - Revision 0.3
8. RECLED operation
The RECLED output pin provides an active-LOW signal, which can be used to drive an LED as a
“record-in-progress” indicator. It returns to a HIGH state when the REC pin is released LOW or when
the recording is completed due to the memory being filled. This pin also pulses LOW to indicate the
end of a message has been reached.
9. ROSC operation
The duration of the device can be varied by changing the value of R2 (R
OSC
). This means the ISD1800
device can actually be between 6 to 16 seconds duration. See the curve below, which charts typical
durations when the R
OSC
is varied from 80 KΩ to 160 KΩ.
This feature allows frequency shifting where a recorded voice or sound can be played back faster or
slower than normal for special effects. For example, use a 100 KΩ resistor to make the recording and
then playback with either an 80 KΩ resistor for faster “chipmunk” talk or with a 120 KΩ resistor for a
slower, lower voice.
Another feature is a “Pause” or interrupt function that can be done by taking the R
OSC
resistor to V
CC
to
stop playback momentarily, resuming when the resistor is connected back to ground.
Chart 1: ISD Duration Versus R
OSC
at T
A
= 25°C and V
CC
= 3.0V
6
8
10
1
2
1
4
1
6
80 100 120 140 160
Typical R
OSC
(K )
Ty
pi
cal
D
u
rat
io
n
(s
ec) I18
10
I18
06
Ω