diff --git a/Makefile b/Makefile
index a7bad8b..adb3a5b 100644
--- a/Makefile
+++ b/Makefile
@@ -20,3 +20,4 @@ TEMPLATES += templates/shutter.substitutions
 
 # Scripts to include in the release
 SCRIPTS += scripts/shutter.cmd
+SCRIPTS += sim/shutter_sim.py
diff --git a/db/readbit.db b/db/readbit.db
index 8b96ac0..623c796 100644
--- a/db/readbit.db
+++ b/db/readbit.db
@@ -1,4 +1,4 @@
-record(bi,"$(PREFIX)$(SPS_REGISTER_NAME):$(BIT_NAME)")
+record(bi,"$(PREFIX):$(SPS_REGISTER_NAME):$(BIT_NAME)")
 {
  field(DTYP, "S7plcFW")
  field(INP,  "@$(SPS_REGISTER_NAME)/$(OFFSET) T=BYTE B=$(BIT)")
diff --git a/db/readstring.db b/db/readstring.db
index df33ef0..a700a3d 100644
--- a/db/readstring.db
+++ b/db/readstring.db
@@ -1,4 +1,4 @@
-record(stringin, "$(PREFIX)$(SPS_REGISTER_NAME):$(STRING_NAME)-Msg")
+record(stringin, "$(PREFIX):$(SPS_REGISTER_NAME):$(STRING_NAME)-Msg")
 {
  field(DTYP, "S7plcFW")
  field(INP,  "@$(SPS_REGISTER_NAME)/$(OFFSET) L=$(LENGTH)")
diff --git a/db/sps_status.db b/db/sps_status.db
index 37f6540..708a3f1 100644
--- a/db/sps_status.db
+++ b/db/sps_status.db
@@ -1,4 +1,4 @@
-record(bi, "$(PREFIX)$(SPS_REGISTER_NAME):ConnStatusFetch")
+record(bi, "$(PREFIX):$(SPS_REGISTER_NAME):ConnStatusFetch")
 {
  field(DTYP, "S7plcFW stat")
  field(INP,  "@$(SPS_REGISTER_NAME)")
@@ -7,7 +7,7 @@ record(bi, "$(PREFIX)$(SPS_REGISTER_NAME):ConnStatusFetch")
  field(SCAN, "I/O Intr")
 }
 
-record(bi, "$(PREFIX)$(SPS_REGISTER_NAME):ConnStatusWrite")
+record(bi, "$(PREFIX):$(SPS_REGISTER_NAME):ConnStatusWrite")
 {
  field(DTYP, "S7plcFW stat2")
  field(INP,  "@$(SPS_REGISTER_NAME)")
diff --git a/db/writebit.db b/db/writebit.db
index 48a6a7e..e55cda8 100644
--- a/db/writebit.db
+++ b/db/writebit.db
@@ -1,4 +1,4 @@
-record(bo, "$(PREFIX)$(SPS_REGISTER_NAME):$(BIT_NAME)")
+record(bo, "$(PREFIX):$(SPS_REGISTER_NAME):$(BIT_NAME)")
 {
  field(DTYP, "S7plcFW")
  field(OUT,  "@$(SPS_REGISTER_NAME)/$(OFFSET) T=BYTE B=$(BIT)")
diff --git a/scripts/shutter.cmd b/scripts/shutter.cmd
index ff3ba52..7b8477e 100644
--- a/scripts/shutter.cmd
+++ b/scripts/shutter.cmd
@@ -11,14 +11,24 @@ require s7plcFW
 #     # out IO Interrupt Delay (if 0 then only reacts on a change)
 # )
 
-epicsEnvSet("SPS_REGISTER_NAME", "$(SPS_REGISTER_NAME=SPS-$(FETCH_DB))")
+epicsEnvSet("SPS_REGISTER_NAME", "SPS-$(FETCH_DB)")
 epicsEnvSet("SPS_FETCH_SIZE", "152")
-epicsEnvSet("SPS_WRITE_SIZE", "1")
+# Seems that 1 doesn't work
+epicsEnvSet("SPS_WRITE_SIZE", "2")
 
-s7plcFWConfigure("$(SPS_REGISTER_NAME)", "$(SPS_IP)", "$(FETCH_PORT=2000),1,$(FETCH_DB),2,$(SPS_FETCH_SIZE)", "$(WRITE_PORT=2001),1,$(WRITE_DB=$(FETCH_DB)),2,$(SPS_WRITE_SIZE)", $(SPS_ENDIANNESS=1), $(SPS_RECEIVE_TIMEOUT=1000), $(SPS_RECEIVE_DELAY=200), 0)
+
+$(SET_SIM_MODE=#) $(SET_SIM_MODE) require misc
+$(SET_SIM_MODE=#) $(SET_SIM_MODE) epicsEnvSet("SPS_IP", "127.0.0.1")
+$(SET_SIM_MODE=#) $(SET_SIM_MODE) system "$(sinqSPS_DIR)shutter_sim.py $(FETCH_PORT=2000) $(WRITE_PORT=2001) &"
+# starting the python socket seems to take a while
+# and need misc to use built in sleep command
+$(SET_SIM_MODE=#) $(SET_SIM_MODE) sleep 3
+
+
+s7plcFWConfigure("$(SPS_REGISTER_NAME)", "$(SPS_IP)", "$(FETCH_PORT=2000),1,$(FETCH_DB),0,$(SPS_FETCH_SIZE)", "$(WRITE_PORT=2001),1,$(WRITE_DB=$(FETCH_DB)),0,$(SPS_WRITE_SIZE)", "$(SPS_ENDIANNESS=1)", "$(SPS_RECEIVE_TIMEOUT=1000)", "$(SPS_RECEIVE_DELAY=200)", "0")
 
 # Provides Connection Status PVs
-dbLoadRecords("$(sinqSPS_DB)/sps_status.db")
+# dbLoadRecords("$(sinqSPS_DB)/sps_status.db", "PREFIX=$(PREFIX), SPS_REGISTER_NAME=$(SPS_REGISTER_NAME)")
 
 # Shutter PVs
-dbLoadTemplate("$(sinqSPS_DB)/shutter.substitions")
+dbLoadTemplate("$(sinqSPS_DB)/shutter.substitutions", "PREFIX=$(PREFIX), SPS_REGISTER_NAME=$(SPS_REGISTER_NAME)")
diff --git a/sim/.__afs7E221F9A5 b/sim/.__afs7E221F9A5
new file mode 100755
index 0000000..afe6af4
--- /dev/null
+++ b/sim/.__afs7E221F9A5
@@ -0,0 +1,13 @@
+#!/usr/local/bin/iocsh  
+
+on error break
+
+require sinqSPS, wall_e
+
+epicsEnvSet("STREAM_PROTOCOL_PATH","./db")
+epicsEnvSet("PREFIX","SQ:TEST")
+
+epicsEnvSet("SET_SIM_MODE","") # Run Shutter Simulation Instead of Connecting with SPS
+runScript "$(sinqSPS_DIR)shutter.cmd" "SPS_IP=127.0.0.1, FETCH_DB=210, FETCH_PORT=2002, WRITE_PORT=2003"
+
+iocInit()
diff --git a/sim/ioc.sh b/sim/ioc.sh
new file mode 100755
index 0000000..ef9bd7f
--- /dev/null
+++ b/sim/ioc.sh
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+export EPICS_HOST_ARCH=linux-x86_64
+export EPICS_BASE=/usr/local/epics/base-7.0.7
+
+PARENT_PATH="$( cd "$(dirname "${BASH_SOURCE[0]}")" ; pwd -P )"
+
+echo "${PARENT_PATH}/st.cmd"
+/usr/local/bin/procServ -L - -f -i ^D^C 20001 "${PARENT_PATH}/st.cmd"
diff --git a/sim/shutter_sim.py b/sim/shutter_sim.py
new file mode 100644
index 0000000..4f52786
--- /dev/null
+++ b/sim/shutter_sim.py
@@ -0,0 +1,92 @@
+#!/usr/bin/env python3
+
+import logging
+import os
+import re
+import socket
+import sys
+import time
+
+from threading import Thread
+
+HOST = "127.0.0.1"  # Localhost
+READ_PORT = int(sys.argv[1])  # Port to listen on
+WRITE_PORT = int(sys.argv[2])  # Port to listen on
+
+LOG2FILE = True # TODO False if len(sys.argv) < 3 else bool(int(sys.argv[3]))
+
+logger = logging.getLogger('shutter')
+
+if LOG2FILE:
+    logging.basicConfig(filename=os.path.join(os.getcwd(), 'shutter_sim.log'), level=logging.INFO)
+
+logger.info(f'Read Requests on {HOST}:{READ_PORT}, Write Requests on {HOST}:{WRITE_PORT}')
+
+def receive(conn, sock_name):
+    # received = conn.recv(1024, socket.MSG_DONTWAIT)
+    received = conn.recv(1024)
+    logger.info(f'RECEIVED on {sock_name}: "{received}"')
+    logger.info('Decimal on %s: %s' % (sock_name, ' '.join(map(str, [received[i+2] for i in range(len(received)-2)]))))
+    return received
+
+def send(conn, data: str):
+    logger.info(f'SENDING: "{data}"')
+    return conn.sendall(data)
+
+def read_requests():
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+
+        s.bind((HOST, READ_PORT))
+        s.listen()
+        conn, _ = s.accept()
+
+        with conn:
+            while True:
+                data = receive(conn, "read")
+
+                # if not data: # Empty implies client disconnected
+                #     break    # Close Server
+
+                try:
+
+                    if data == b'':
+                        send(conn, b'')
+
+                    elif len(data) == 14 and data[0] == 83 and data[1] == 53:
+                        # Trying to fetch data
+                        org = data[8]
+                        db = data[9]
+                        s7addr = data[10] * 256 + data[11]
+                        s7len = data[12] * 256 + data[13]
+                        logger.info(f'Fetch: db: {db}, address: {s7addr}, total: {s7len}')
+
+                        send(conn, b'0' * s7len)
+
+                except Exception as e:
+                    logger.exception('Simulation Broke')
+                    # send('?OV')
+
+def write_requests():
+
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+
+        s.bind((HOST, WRITE_PORT))
+        s.listen()
+        conn, _ = s.accept()
+
+        with conn:
+            while True:
+                data = receive(conn, "write")
+
+                # if not data: # Empty implies client disconnected
+                #     break    # Close Server
+
+
+read_thread = Thread(target=read_requests)
+write_thread = Thread(target=write_requests)
+
+read_thread.run()
+write_thread.run()
+
+while True:
+    pass
diff --git a/sim/st.cmd b/sim/st.cmd
new file mode 100755
index 0000000..6a1dcb5
--- /dev/null
+++ b/sim/st.cmd
@@ -0,0 +1,13 @@
+#!/usr/local/bin/iocsh  
+
+on error break
+
+require sinqSPS, wall_e
+
+epicsEnvSet("STREAM_PROTOCOL_PATH","./db")
+epicsEnvSet("PREFIX","SQ:TEST")
+
+epicsEnvSet("SET_SIM_MODE","") # Run Shutter Simulation Instead of Connecting with SPS
+runScript "$(sinqSPS_DIR)shutter.cmd" "SPS_IP=127.0.0.1, FETCH_DB=210, FETCH_PORT=2030, WRITE_PORT=2031"
+
+iocInit()