Semiconductor Group

4

Circuit Description

Trigger

Positive pulses on inputs E1 and/or E2 trigger the IC. The hold feedback in the logic has a delay of

several milliseconds. After this delay has elapsed, the tone sequence is started. This prevents

parasitic spikes from producing any effect on the trigger pins.

The following table shows the trigger options:

Oscillator

This is a precision triangle oscillator with an external time constant (R x C). Capacitor

C

is charged by constant current to 1 V and then discharged to 0.5 V. The constant current is obtained

on pin

R

When the voltage on

C

complete tone sequence is issued. If the oscillator pin is short-circuited to GND during operation,

the sequence is repeated.

Voltages on Pin

C

OSC

E1

E2

Mode

Issued Sequence

Triggered

Triggered

Triple-tone

Minor and major third

Grounded/open

Triggered

Dual-tone

Minor third

Triggered

Grounded/open

Single-tone

1st tone of minor third

The following applies:

∆V

f

SAE 800