Sine Systems RFC-1/B Instruction Book

Speech Out
(optional)
DTMF Tones In -----
To "TELEPHONE" Jack
Cl and C2 are 2 pF, 200 volt film capacitors and T1 and T2 are 600 ohm to 600 ohm
transformers, such as a Prem SPT-124. This circuit could be used with a two-way radio, a
voice pager, an SCA/STL subchannel, or just about any communications link capable of
passing voice-grade audio. It is important to remember that operation of the RFC- 1 from this
port does not require the entry of the security code so the communications link itself should
be reasonably secure. Also keep in mind that the dedicated control mode will be entered with
the detection of any DTMF tones at the dedicated control port, so spurious DTMF tones, or
DTMF tones used for other purposes should not appear at this port. The RFC-l's speech
synthesizer is active on the dedicated control port at all times and telemetry readings will be
spoken as the RFC-1 makes the initial measurements for the Telephone Alarm System, if
activated, as well as for subsequent check-scans.
The proper audio level needed at the dedicated control port can be determined by
experimentation and should be adjusted to the minimum level required for reliable operation.
In the above circuit, higher value resistors may be substituted but do not use series resistors
less than 3.3K ohms if two transformers are used, or less than 1.5K ohms if one transformer
is used.
Audio Detection
In some cases it may be desirable to be able to monitor the presence of an audio signal. For
example, absence of audio at the output of a modulation monitor could be made to trigger the
telephone alarm system. Here is the schematic for a simple audio detector:
DC Output
(To RP-8 Panel)
R1 is 470 ohms (Radio Shack 271-1317), DI and D2 are 1N4001 (Radio Shack 276-1101), and
Cl and C2 are 470 pF/ 16V (Radio Shack 272-957). Any audio level of -6 dBv or greater will
maintain at least 0.5 volts DC at the output. This covers most "line level" audio sources.
3.00.2
Installation
page 5.14

Sine Systems RFC-1/B Specifications

General

Brand	Sine Systems
Model	RFC-1/B
Category	Remote Control
Language	English