Two Tone Paging Encoder

TS-1 Sub-Audible Encoder-Decoder • Microminiature in size. 1.25 x 2.0'x .65 • Encodes and decodes simultaneously • $59.95 complete with K-1 element

TS-1 JR Sub-Audible Encoder-Decoder • Microminiature version of the TS-1 measuring just 1.0* x 1 25 x .65" for handheld units • $79.95 complete with K-1 element

ME-3 Sub-Audible Encoder • Microminiature in size, measures 45 x 1.1 x 6 • Instant start-up • $29.95 complete with K-1 element

TE-8 Eight-Tone Sub-Audible Encoder • Measures 2.6" x 2.0* x .7 • Frequency selection made by either a pull to ground or to supply • $69.95 with 8 K-1 elements.

PE-2 Two-Tone Sequential Encoder for paging • Two call unit • Measures 1.25" x 2.0'x.65' • $49.95 with2K-2elements

SD-1 Two-Tone Sequential Decoder • Frequency range is 268 5-2109 4 Hz • Measures 1.2' x 167' x 65' • Momentary output for hom relay, latched output for call light and receiver muting built-in • $59.95 with 2 K-2 elements.

TE-12 Twelve-Tone Sub-Audible or Burst-Tone Encoder • Frequency range is 67.0-263.0 Hz sub-audible or 1650-4200 Hz burst-tone • Measures 4.25* x 2.5" x 1.5* • $79.95 with 12 K-1 elements

ST-1 Burst-Tone Encoder • Measures 95 x 5x5 plus jjjb

K-1 measurements • Frequency range is 1650-4200 Hz • ^


m^mg 426 West Ta<t Avenue. Orange, CA 92667 IHf (800) 854 0547. California residents use: (714) 998-3021

The Italian Freq Generator

— from Bologria to you

A few years ago, this generator's qualities were found only in expensive, lab-type gear.

Louis /. Hut ion K1YIL 12235 S.E. 62nd Street Betlevue WA 98006

During my recent visit to Sr. Franco Fanti l4LCF's ham shack, I was looking over his latest issues of an Italian elec tronics magazine called CQ Eiettronica.1 In the May, 1977, issue, t found a very interesting article on a phase locked digital signal generator.2 I obtained a copy of that article and laboriously translated the major portion of it to get an idea of what the author, Sr. Mario Scarpelli I6IHB, had to say regarding the unit. This looked to me like it was just what I needed in the way of a home-brewed signal generator to replace my aging Heathkit AG-1 audio signal generator.

An undrilled, blank PC board was obtained through I4LCFJJ and a model was constructed in my shop lhe generator provides a square wave

Encoder Stereo

from 1 Hz to 9.999 MHz at a TTL output level. The signal may be switched on and off through the control input port.

Circuit Description

The digital signal generator consists of six basic components as shown in the block diagram (Fig, 4). The circuit is basically a phase locked loop design with the oscillator searching through its frequency spectrum until it finds the frequency selected in the programmable counter. At this point, the loop locks. To expand the range of the unit's frequency coverage, !6THB added a logic detector circuit that enables the voltage-controlled multivibrator to switch to a different frequency range by changing the value of the frequency-determining capacitor.

The reference oscillator consists of a 1 MHz crystal oscillator. X1 (7400), with three frequency dividers, X2, X3, and X4 (7490) The resulting output frequency of 1 kHz from the divider is used as a reference signal in the phase detector, XI3 (MC4044).

Four thumbwheel binary-coded decimal (BCD) switches are used in combination with four 74192s, X5, X6, X7, and X8, dividers to provide a programmable counter. The four 7400s, X9, XI0, X11. and X12, are buffer/inverters to provide the proper TTL state to the inputs of the 74192 dividers. The thumbwheel switches cover an input range of from 0000 to 9999, The output from the programmable counter is connected to the phase detector, X13.

The frequency range logic detector consists of XI5, XI6, and X17. This circuit js connected to selected segments of the BCD switches so that, between 0000 and 3399, the VCM frequency-determining capacitor is 133 pF. From 3400 to 9999, the capacitor is reduced to 33 pF by the switching relay, RY-1,

The phase detector, X17 (MC4044), compares the reference oscillator signal with the output signal from the programmable divider and converts this to a dc voltage level proportional to the phase error. This error voltage is fed to the input of the VCM, X14 (MC4024), to drive or hold it to the frequency displayed on the thumbwheel switches.

The output of the VCM is connected to the input of the programmable counter to complete the phase locked loop circuit, The output signal is also connected to the input of the output frequency selectable divider chain consisting of X18, XI9, X21, X22, X23, and X24 (7490). The MULTIPLY-BY selector switch is used to expand the digits appearing on the thumbwheel switches into the desired frequency. For example, 2125 appearing



Programmable Divider With 74192

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