Section 365-262-205
5
4.
CIRCUIT DESCRIPTION
Refer to Figure 6 and Figure 7 for the block diagrams, as needed, while reading the following circuit description.
Notes are explained in Table 2.
4.1
Transmit Voice Path
Voice Frequency (VF) signals applied to the T&R leads (pins 50 and 48) are routed through transformer T1 to the
XMT GAIN circuit.
The amplified VF signal is then applied to the XMT PRESCRIPTION GAIN circuit. This circuit provides up to
32.5dB of gain in increments of 0.1dB to accommodate input Transmission Level Points (TLPs) between
–22.5dBm and +10dBm.
Following the XMT PRESCRIPTION GAIN circuit, the VF signal is passed to the XMT FILTER and the ENCOD-
ER circuits. The XMT FILTER attenuates frequencies outside the bandwidth of a standard voice channel and pre-
vents it from passing into the ENCODER. The ENCODER converts the analog VF signal to a digital signal and
applies it to the XDATA lead for transmission to the line.
4.2
Receive Voice Path
Digital signals received at the RDATA lead are applied to the DECODER and the RCV FILTER circuits for conver-
sion to an analog signal and attenuation of frequencies outside the bandwidth of a standard voice channel. The
output of the RCV FILTER circuit is routed to the RCV PRESCRIPTION GAIN.
The RCV PRESCRIPTION GAIN circuit provides up to 32.5dB of gain in increments of 0.1dB to accommodate
output TLPs between –22.5dBm and +10dBm.
The RCV GAIN circuit amplifies the adjusted VF signal output from the RCV PRESCRIPTION GAIN circuit to the
T1 and R1 leads (pins 8 and 7) via transformer T2.
4.3
Signaling
The channel unit’s signaling path interfaces with the CO trunk circuit via the E- and M-leads (pins 4 and 45). The
M-lead signal output by the CO trunk circuit passes through the NORM/BUSY switch and into the M-LEAD DE-
TECTOR circuit.
4.3.1.
E&M Signaling (Transmit)
In E&M signaling, an off-hook condition (-battery) on the M-lead is applied to the M-LEAD DETECTOR circuit via
the NORM/BUSY switch. This causes a logic 1 state to be transmitted by the ENCODER on both A and B signal-
ing highways with the outgoing bit stream via the XDATA lead, indicating a busy condition on the channel circuit.
An on-hook condition (ground/open) causes a logic 0 state to be transmitted with the outgoing bit stream and indi-
cates a channel idle condition.
4.3.2.
E&M Signaling (Receive)
The information received via the carrier facility appears on the RDATA lead. An off-hook condition (logic 1 state
on A signaling highway) detected by the DECODER circuit will cause the E RELAY to operate and the BUSY LED
to illuminate, indicating a busy condition (ground or loop) on the E-lead. An on-hook condition (logic 0 state on A
signaling highway) detected by the DECODER circuit will cause the E RELAY to release and the BUSY LED to
extinguish, indicating an idle condition (open) on the E-lead.
4.3.3.
E2M2 Signaling (3652–62 Only)
The E&M signaling pair of the E2M2 channel unit operate in a similar manner as those described in Paragraphs
3.09 and 3.10, except the A and B signaling highways operate independently of each other. (M-lead signaling is
applied to only the A highway; M2-lead signaling is applied to only the B highway). The E2 and M2 signaling pair
can be used for tandem FX, alarm monitoring, or toll-ticketing applications, and utilizes –48V for the M2-lead busy
status and ground or open for the M2-lead idle status.
4.3.4.
M2-Lead Signaling (Transmit)
A busy condition (-battery) applied to the M2-lead is routed to the M2-LEAD DETECTOR. The M2-LEAD DETEC-
TOR circuit applies an input signal to the ENCODER, which causes a logic 1 state to be transmitted on the B
highway with the outgoing bit stream via the XDATA lead. A ground or open applied to the M2-lead causes a logic
0 state to be transmitted with the outgoing bit stream.
