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 14 (973)
334-3100
FUNCTIONAL DESCRIPTION
SYSTEM OVERVIEW
The VF-8A is a two-wire Orderwire Voice Frequency Channel Module designed for RFL IMUX 2000
T1 and E1 multiplexers. The VF-8A provides a very reliable means of voice communication between
multiple locations. Figure 3 is a simplified block diagram of the RFL VF-8A module.
The VF-8A accepts a single voice channel as input and uses u-law PCM (CODEC) encoding to convert
the analog voice into an 8-bit, 64-Kbps digital signal. All of the VF-8A settings can be configured via
local switches or remotely with use of the RFL SCL (Simple Command Language).
The VF-8A uses two signaling bits of the T1/E1 data stream. One is used to indicate a busy circuit, and
the other is used to indicate ringing. Channel-Associated Signaling (CAS) is used in E1 applications,
while Robbed-Bit Signaling (RBS) is used in T1 applications. A “signaling delay” is available for
switching networks; i.e. containing RFL Mini-DACS module.
The VF-8A allows the use of Dual-Tone Multi-Frequency (DTMF) telephones to selectively place a
call between any or all locations within the RFL orderwire network. The three levels of DTMF
signaling include “Unique”, “Group”, and “All” call.
Call progress tones are provided to indicate phone ringing, circuit busy, circuit available, and phone
out-of-service. These give the VF-8A the “feel” of a real phone instead of a party line.
Three busy circuit modes are available. The level of privacy that the local extension maintains depends
on the setting of each remote extension.
A “timeout” feature is included to free up the network for other calls if a phone is inadvertently left in
the off-hook condition for a period exceeding 50 seconds.
BACKPLANE AND POWER CONNECTIONS
The VF-8A occupies a single physical slot in the multiplexer and conforms to the RFL IMUX 2000
backplane signal format. All T1 and E1 backplane signals in and out of the VF-8A have drivers with
hot-pluggable capability. Control signals passing through the backplane from the I/O to the VF-8A
module are pulled up to +5V through 10 K Ohm resistors.
The VF-8A requires digital +5V, analog ±15V, -48V, and analog and digital ground. The IMUX 2000
Power Supply provides these. The –48V can be supplied by an optional external 48V talk battery. The
+5 digital volt input includes an inductor which lowers the inrush current to prevent power interruption
during module insertion, and also prevents high frequency noise to be injected into the VF-8A by other
modules. The digital +5V supply is used to power the Actel FPGA and driver ICs. TP1 is the ground
test point situated near the fingers of the module where digital and analog grounds are referenced to one
another. The digital +5V and analog ±15V from the backplane are routed to the Hot Swap Controller.
This device, and surrounding circuitry control the ramp of the power to all of the ICs.
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