implemented loopback option SRM

html_orig/pages/cfg_term.php

@@ -152,6 +152,12 @@
 		<input type="hidden" id="show_config_links" name="show_config_links" value="%show_config_links%">
 	</div>
 
+	<div class="Row checkbox" >
+		<label><?= tr('term.loopback') ?></label><!--
+		--><span class="box" tabindex=0 role=checkbox></span>
+		<input type="hidden" id="loopback" name="loopback" value="%loopback%">
+	</div>
+
 	<div class="Row buttons">
 		<a class="button icn-ok" href="#" onclick="qs('#form-2').submit()"><?= tr('apply') ?></a>
 	</div>

html_orig/pages/help/cmd_system.php

@@ -74,6 +74,18 @@
 					Show (`h`) or hide (`l`) menu/help links under the screen.
 				</td>
 			</tr>
+			<tr>
+				<td>
+					<code>
+						\e[12h \\
+						\e[12l
+					</code>
+				</td>
+				<td>
+					Enable (`h`) or disable (`l`) Send-Receive Mode (SRM).
+					SRM is the opposite of Local Echo, meaning `\e[12h` disables and `\e[12l` enables Local Echo.
+				</td>
+			</tr>
 			<tr>
 				<td>`\e[8;<i>r</i>;<i>c</i>t`</td>
 				<td>Set screen size (this is a command borrowed from xterm)</td>