Section 365-361-206
5
NOTES (CONTINUED):
+10
+ 7
0
16
22.5
INPUT (dBm) XMT GAIN (dB)
12. The XMT INPUT range at T&R: 22.5dBm to +10dBm. The
unit is factory adjusted for 16dBm input, with the XMT
gain set to 26dB.
0
3
10
26
32.5
+10
+ 7
0
16
22.5
OUTPUT (dBm) RCV GAIN (dB)
32.5
29.5
22.5
6.5
0
14. The RCV OUTPUT range at T1&R1: 22.5dBm to
+10dBm. The unit is factory adjusted for +7dBm output,
with the RCV gain set to 29.5dB.
13. The XMT PRESCRIPTION circuit provides 32.5dB gain in
0.1dB steps to compensate for input level variations. ReĆ
fer to the following table for details:
15. The RCV PRESCRIPTION circuit provides 32.5dB gain in
0.1dB steps to compensate for office wiring loss and outĆ
put level variations. Refer to the following table for details:
16. Trunk process relay is activated immediately due to an
alarm condition in the channel bank. Two seconds later it is
deactivated for 70 milliseconds and again activated. During
the activated mode, leads designated as 1 and 2 are
shorted:
Lead 2 Ground Close Y
Lead 2 Open Open Y
17. When the channel unit is removed from its mounting
slot, the lead designated 1" (pin 2) is grounded
through a shorting contact in the card connector.
18. When the channel unit is shipped from the factory the
default setting is for 7 5/6 bit encoding and decoding
and to send a busy" to the far end on both signaling
highways. For full 8Ćbit conversion, cut the jumper
wire at XC (encoding) and YC (decoding).
Figure 5. 3653–61 (Issue 6) 4W TO W/ER Block Diagram (Part 2 of 2)
4. CIRCUIT DESCRIPTION
Refer to Figure 5, the 3653–61 (Issue 6) block diagram, as needed while reading the following circuit description.
4.1 Transmit VF Path
VF signals applied to the input T&R (pins 50 and 48) are routed through the DROP and LINE lifting jacks to trans-
former T1. Transformer T1 provides a balanced input and dc isolation from the line.
Voice energy from transformer T1 is routed into the XMT GAIN and XMT PRESCRIPTION GAIN circuits which,
acting together, set the receive path gain to the exact level required to drive the XMT FILTER and ENCODER
circuits. The use of the XMT PRESCRIPTION GAIN allows finely controlled adjustment (0.1dB increments) for a
range of office TLPs from +10 to –22dBm.
The adjusted VF signal is then applied to the XMT FILTER circuit. The filter suppresses frequencies that are out-
side of the standard voice frequency and prevents them from entering the ENCODER. The ENCODER performs
an analog-to-digital (A/D) conversion of the VF signal before applying it to the XDATA lead for transmission to the
far end. The encoded bit stream can be selected for either a 7 5/6-bit or a full 8-bit encoding via wire jumper XC.
Selecting the 7 5/6-bit encoding sends a busy signal to the far end at all times. Selecting the full 8-bit encoding
provides for a greater signal-to-noise ratio.
4.2 Receive VF Path
The preselected 7 5/6-bit or full 8-bit digital signal transmitted from the far end is received by the 3653–61 via the
RDATA lead and is applied to the DECODER circuit. The DECODER performs a digital-to-analog (D/A) conver-
sion of the signal. To properly decode the information received, wire jumper YC is provided to match the decoding
scheme of the receive path to the scheme that was selected for the transmit path of the channel unit at the far
end. From the DECODER circuit, signals are passed to the RCV FILTER. The RCV FILTER suppresses frequen-
cies that are outside the bandwidth of the standard voice band.
The output of the RCV FILTER is applied to the RCV GAIN and RCV PRESCRIPTION GAIN circuits which, act-
ing together, set the receive path gain to the exact level required to interface with a range of office TLPs. The use
