diff --git a/RPi_utils/send.cpp b/RPi_utils/send.cpp
index a291051..575f27e 100644
--- a/RPi_utils/send.cpp
+++ b/RPi_utils/send.cpp
@@ -15,14 +15,34 @@ int main(int argc, char *argv[]) {
      for pin mapping of the raspberry pi GPIO connector
      */
     int PIN = 0;
+    const char* code[6] = { "00000", "10000", "01000", "00100", "00010", "00001" };
+
+    if (argc < 4) {
+        printf("Sending 433 MHz remote plug control codes, hardcoded on wiringpi pin %d.\n", PIN);
+        printf("Usage: %s <systemCode> <unitCode> <command> [pulseLength]\n", argv[0]);
+        printf("systemCode  - First five settings of Type A 10 pole DIP switch, e.g. 11111\n");
+        printf("unitCode    - Switch number [1 .. 5] or [10000 .. 00001]\n");
+        printf("command     - 0 for OFF and 1 for ON\n");
+        printf("pulseLength - optional pulse length\n");
+        return -1;
+    }
+
     char* systemCode = argv[1];
-    int unitCode = atoi(argv[2]);
+    const char* unitCode;
+    if (strlen(argv[2]) == 5) {
+        unitCode = argv[2];
+    } else if (atoi(argv[2]) > 0 and atoi(argv[2]) < 6) {
+        unitCode = code[atoi(argv[2])];
+    } else {
+        return -1;
+    }
     int command  = atoi(argv[3]);
-    
+
     if (wiringPiSetup () == -1) return 1;
-    printf("sending systemCode[%s] unitCode[%i] command[%i]\n", systemCode, unitCode, command);
+    printf("sending systemCode[%s] unitCode[%s] command[%i]\n", systemCode, unitCode, command);
     RCSwitch mySwitch = RCSwitch();
-    if (argv[4] != NULL) mySwitch.setPulseLength(atoi(argv[4]));
+    if (argv[4] != NULL)
+        mySwitch.setPulseLength(atoi(argv[4]));
     mySwitch.enableTransmit(PIN);
     
     switch(command) {