Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
RFL VF-8A RFL Electronics Inc.
August 6, 2010 17 (973)
334-3100
RECEIVE SECTION
The VF-8A receives an 8-bit, 64-Kbps digital signal from the appropriate bus and timeslot. The input
signals go to the Logic Array where they are processed and de-multiplexed. The 8-bit digital output of
the Logic Array is then converted to an analog audio signal by the u-law PCM CODEC and is passed to
the analog switch, and the DTMF decoder. If the RX TONE EN signal applied to the analog switch is
inactive, the audio signal passes through the stereo volume control, trans-hybrid circuit, SLIC, and rear
backplane to the MA-306 I/O. For any voice or audio tone to pass through the SLIC, the local phone
must be off-hook and the SLIC must be programmed for “Active” mode by inputs C1 and C2.
The DTMF decoder monitors all tones received from the CODEC generated by the remote telephone
keypads. If a valid DTMF tone is detected which lasts for the required interval, the STD signal will
clock out the BCD equivalent of the tone detected, into the Logic Array. It is necessary to monitor
remote tones in order for the supporting local DTMF logic to determine whether the “Unique” station,
“All”, and “Group” is a match. Once a DTMF match is determined by the logic, the SLIC is
programmed for “Ring” mode by inputs C1 and C2. The amber RING LED will illuminate,
corresponding to the ring cadence of 2 Sec ON and 4 Sec OFF.
In addition to audio tones and voice received from remote locations, locally generated tones are
received. TONE 0 and TONE 1 digital signals are generated by the Logic Array at specific
frequencies. These signals pass through low-pass filters before being summed by an operational
amplifier. An active RX TONE EN signal from the Logic Array is applied to the analog switch which
selects the tone to be received and not the remote voice input signal. The tone is passed through the
stereo volume control , trans-hybrid circuit, SLIC, and rear backplane to the MA-306 I/O similar to the
remote voice input. Received tones include ring back, dial, busy, and re-order.
Signaling information from remote VF-8As are also received. The remote “ring” and “connection”
states are received from the appropriate bus(s) into the proper timeslot. If the local phone has dialed
the remote phone(s), the received “ring” signal indicates the ring period. This is especially important
as the locally generated ring back tone is used when a “group” or “all” call is initiated; the remote
phones do not generate the ring tone. The first phone to be off-hook always makes “connection” by
default. The green BUSY LED will illuminate at both local and remote locations. If that phone dials
the remote phone(s), and a phone goes off-hook, it also has made “connection”. The local phone in the
off-hook condition will “timeout” after 50 seconds if neither “ring” nor “connection” are received. A
local re-order tone will be generated and the circuit will be freed up for other calls. If local and remote
phones are all on-hook, the SLIC(s) are programmed for “open circuit” mode by inputs C1 and C2.
ALERTS/ALARMS
The RFL VF-8A module reports no module level ALERT or ALARM signals to the shelf Common
Module.
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