External Frequency Counter; Feeding-Back Protection (Option) - Toellner Toe 7704 Bedienungsanleitung

sinusoidal 1 kHz signal. An external signal can be added
to this internal modulation signal via the EXT IN input.
The modulation depth can be varied between 0 % to
100 % using the MODULATION control.
The internal modulation source is switched off when the
key is in the "External" position, and only
INT/EXT
external modulation is possible via the EXT IN input.
The level of the carrier can now be additionally changed
in the range from 0 % to 100 % using the
AM CARRIER LEVEL control so that external modula-
tion with a suppressed carrier can be set. The correlation
between the MODULATION and AM CARRIER LEVEL
controls is such that, with 100 % modulation and 50 %
carrier, an external modulation signal of 5 V
a standard amplitude-modulated signal with a modula-
tion depth of 100 % at the main output OUTPUT.

2.3.11 External Frequency Counter

The external frequency counter is activated by
switching the key to the state "External" if the
INT/EXT
FUNCTION switch is not in the position DC/AMPL and
the device is set to free-running generator mode or to
PLL mode both with frequency display. When in oper-
ating mode DC/AMPL it is possible to switch to external
frequency counter mode by changing the switch
position DC/AMPL of the FUNCTION switch to one of
the standard signal functions if external frequency coun-
ter mode was active before switching to DC/AMPL.
A TTL signal with the frequency of approx. 10 Hz to
50 MHz applied to the input socket EXT IN is counted
by the integrated frequency counter which operates with
26
a reciprocal counting procedure, and the result is dis-
played with a resolution of 4 digits and autoranging.
The measurement time is approx. 0.5 s.

2.3.12 Feeding-back Protection (Option)

The function generators TOE 7704 to TOE 7711A with
optionally equipped feeding-back protection obtain an
improved safety against unintended external voltage fed
into the output connector OUTPUT. The output is pro-
tected from voltage applied up to ± 120 V. The equip-
ment includes a fuse to protect the internal electronical
circuitry, which might be blown if a low-impedance
voltage source is connected to the output. In this case no
generates
PP
signal will be occur at the output afterwards.
To replace the fuse, all connections to or from the func-
tion generator must be cut. The mains supply must be
disconnected from the device. Then unscrew the upper
two of the four screws on each side of the cabinet and
remove the top cover. The feeding-back protection cir-
cuitry is mounted near the front panel between the out-
put-amplifier heat sink and the right hand side wall. The
fuse holder is assembled between the heat sink, the side
wall and the front circuit boards and can be easily
opened by employing a screw driver.
After having replaced the fuse (type of fuse → 2.4
Technical Data) assemble the cabinet in the reverse
order, restore the former connections and the function
generator will be ready for operation again.
TOELLNER Electronic Instrumente GmbH