diff --git a/docs/topics/signals.rst b/docs/topics/signals.rst
index 2def53848..8661f86a0 100644
--- a/docs/topics/signals.rst
+++ b/docs/topics/signals.rst
@@ -16,8 +16,7 @@ deliver the arguments that the handler receives.
 You can connect to signals (or send your own) through the
 :ref:`topics-api-signals`.
 
-Here is a simple example showing how you can catch signals and perform some action:
-::
+Here is a simple example showing how you can catch signals and perform some action::
 
     from scrapy import signals
     from scrapy import Spider
@@ -52,9 +51,45 @@ Deferred signal handlers
 ========================
 
 Some signals support returning :class:`~twisted.internet.defer.Deferred`
-objects from their handlers, see the :ref:`topics-signals-ref` below to know
-which ones.
+objects from their handlers, allowing you to run asynchronous code that
+does not block Scrapy. If a signal handler returns a
+:class:`~twisted.internet.defer.Deferred`, Scrapy waits for that
+:class:`~twisted.internet.defer.Deferred` to fire.
 
+Let's take an example::
+
+    class SignalSpider(scrapy.Spider):
+        name = 'signals'
+        start_urls = ['http://quotes.toscrape.com/page/1/']
+
+        @classmethod
+        def from_crawler(cls, crawler, *args, **kwargs):
+            spider = super(SignalSpider, cls).from_crawler(crawler, *args, **kwargs)
+            crawler.signals.connect(spider.item_scraped, signal=signals.item_scraped)
+            return spider
+
+        def item_scraped(self, item):
+            # Send the scraped item to the server
+            d = treq.post(
+                'http://example.com/post',
+                json.dumps(item).encode('ascii'),
+                headers={b'Content-Type': [b'application/json']}
+            )
+
+            # The next item will be scraped only after
+            # deferred (d) is fired
+            return d
+
+        def parse(self, response):
+            for quote in response.css('div.quote'):
+                yield {
+                    'text': quote.css('span.text::text').get(),
+                    'author': quote.css('small.author::text').get(),
+                    'tags': quote.css('div.tags a.tag::text').getall(),
+                }
+
+See the :ref:`topics-signals-ref` below to know which signals support
+:class:`~twisted.internet.defer.Deferred`.
 
 .. _topics-signals-ref:
 
@@ -66,9 +101,12 @@ Built-in signals reference
 
 Here's the list of Scrapy built-in signals and their meaning.
 
-engine_started
+Engine signals
 --------------
 
+engine_started
+~~~~~~~~~~~~~~
+
 .. signal:: engine_started
 .. function:: engine_started()
 
@@ -81,7 +119,7 @@ engine_started
     getting fired before :signal:`spider_opened`.
 
 engine_stopped
---------------
+~~~~~~~~~~~~~~
 
 .. signal:: engine_stopped
 .. function:: engine_stopped()
@@ -91,9 +129,20 @@ engine_stopped
 
     This signal supports returning deferreds from their handlers.
 
-item_scraped
+Item signals
 ------------
 
+.. note::
+    As at max :setting:`CONCURRENT_ITEMS` items are processed in
+    parallel, many deferreds are fired together using
+    :class:`~twisted.internet.defer.DeferredList`. Hence the next
+    batch waits for the :class:`~twisted.internet.defer.DeferredList`
+    to fire and then runs the respective item signal handler for
+    the next batch of scraped items.
+
+item_scraped
+~~~~~~~~~~~~
+
 .. signal:: item_scraped
 .. function:: item_scraped(item, response, spider)
 
@@ -112,7 +161,7 @@ item_scraped
     :type response: :class:`~scrapy.http.Response` object
 
 item_dropped
-------------
+~~~~~~~~~~~~
 
 .. signal:: item_dropped
 .. function:: item_dropped(item, response, exception, spider)
@@ -137,7 +186,7 @@ item_dropped
     :type exception: :exc:`~scrapy.exceptions.DropItem` exception
 
 item_error
-------------
+~~~~~~~~~~
 
 .. signal:: item_error
 .. function:: item_error(item, response, spider, failure)
@@ -159,8 +208,11 @@ item_error
     :param failure: the exception raised
     :type failure: twisted.python.failure.Failure
 
+Spider signals
+--------------
+
 spider_closed
--------------
+~~~~~~~~~~~~~
 
 .. signal:: spider_closed
 .. function:: spider_closed(spider, reason)
@@ -183,7 +235,7 @@ spider_closed
     :type reason: str
 
 spider_opened
--------------
+~~~~~~~~~~~~~
 
 .. signal:: spider_opened
 .. function:: spider_opened(spider)
@@ -198,7 +250,7 @@ spider_opened
     :type spider: :class:`~scrapy.spiders.Spider` object
 
 spider_idle
------------
+~~~~~~~~~~~
 
 .. signal:: spider_idle
 .. function:: spider_idle(spider)
@@ -228,7 +280,7 @@ spider_idle
     due to duplication).
 
 spider_error
-------------
+~~~~~~~~~~~~
 
 .. signal:: spider_error
 .. function:: spider_error(failure, response, spider)
@@ -246,8 +298,11 @@ spider_error
     :param spider: the spider which raised the exception
     :type spider: :class:`~scrapy.spiders.Spider` object
 
+Request signals
+---------------
+
 request_scheduled
------------------
+~~~~~~~~~~~~~~~~~
 
 .. signal:: request_scheduled
 .. function:: request_scheduled(request, spider)
@@ -264,7 +319,7 @@ request_scheduled
     :type spider: :class:`~scrapy.spiders.Spider` object
 
 request_dropped
----------------
+~~~~~~~~~~~~~~~
 
 .. signal:: request_dropped
 .. function:: request_dropped(request, spider)
@@ -281,7 +336,7 @@ request_dropped
     :type spider: :class:`~scrapy.spiders.Spider` object
 
 request_reached_downloader
----------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 .. signal:: request_reached_downloader
 .. function:: request_reached_downloader(request, spider)
@@ -297,7 +352,7 @@ request_reached_downloader
     :type spider: :class:`~scrapy.spiders.Spider` object
 
 request_left_downloader
------------------------
+~~~~~~~~~~~~~~~~~~~~~~~
 
 .. signal:: request_left_downloader
 .. function:: request_left_downloader(request, spider)
@@ -315,8 +370,11 @@ request_left_downloader
     :param spider: the spider that yielded the request
     :type spider: :class:`~scrapy.spiders.Spider` object
 
+Response signals
+----------------
+
 response_received
------------------
+~~~~~~~~~~~~~~~~~
 
 .. signal:: response_received
 .. function:: response_received(response, request, spider)
@@ -336,7 +394,7 @@ response_received
     :type spider: :class:`~scrapy.spiders.Spider` object
 
 response_downloaded
--------------------
+~~~~~~~~~~~~~~~~~~~
 
 .. signal:: response_downloaded
 .. function:: response_downloaded(response, request, spider)