diff --git a/src/mess/drivers/a6809.c b/src/mess/drivers/a6809.c
index 59b13210a2e..55ac980a4e9 100644
--- a/src/mess/drivers/a6809.c
+++ b/src/mess/drivers/a6809.c
@@ -85,6 +85,7 @@ public:
 private:
 	UINT8 m_cass_data[4];
 	bool m_cass_state;
+	bool m_cassold;
 	UINT8 m_video_index;
 	required_device<via6522_device> m_via;
 	required_device<cassette_image_device> m_cass;
@@ -197,6 +198,12 @@ TIMER_DEVICE_CALLBACK_MEMBER(a6809_state::a6809_c)
 {
 	m_cass_data[3]++;
 
+	if (m_cass_state != m_cassold)
+	{
+		m_cass_data[3] = 0;
+		m_cassold = m_cass_state;
+	}
+
 	if (m_cass_state)
 		m_cass->output(BIT(m_cass_data[3], 0) ? -1.0 : +1.0); // 2400Hz
 	else
diff --git a/src/mess/drivers/acrnsys1.c b/src/mess/drivers/acrnsys1.c
index 3bf65b72396..f08d8ee8e8e 100644
--- a/src/mess/drivers/acrnsys1.c
+++ b/src/mess/drivers/acrnsys1.c
@@ -78,6 +78,7 @@ private:
 	UINT8 m_digit;
 	UINT8 m_cass_data[4];
 	bool m_cass_state;
+	bool m_cassold;
 };
 
 
@@ -116,6 +117,12 @@ TIMER_DEVICE_CALLBACK_MEMBER(acrnsys1_state::acrnsys1_c)
 {
 	m_cass_data[3]++;
 
+	if (m_cass_state != m_cassold)
+	{
+		m_cass_data[3] = 0;
+		m_cassold = m_cass_state;
+	}
+
 	if (m_cass_state)
 		m_cass->output(BIT(m_cass_data[3], 0) ? -1.0 : +1.0); // 2400Hz
 	else
diff --git a/src/mess/drivers/alphatro.c b/src/mess/drivers/alphatro.c
index f585d235a51..785a4b3d09d 100644
--- a/src/mess/drivers/alphatro.c
+++ b/src/mess/drivers/alphatro.c
@@ -86,6 +86,7 @@ private:
 	UINT8 m_timer_bit;
 	UINT8 m_cass_data[4];
 	bool m_cass_state;
+	bool m_cassold;
 	emu_timer* m_sys_timer;
 	virtual void video_start();
 	virtual void machine_start();
@@ -434,6 +435,12 @@ TIMER_DEVICE_CALLBACK_MEMBER(alphatro_state::alphatro_c)
 {
 	m_cass_data[3]++;
 
+	if (m_cass_state != m_cassold)
+	{
+		m_cass_data[3] = 0;
+		m_cassold = m_cass_state;
+	}
+
 	if (m_cass_state)
 		m_cass->output(BIT(m_cass_data[3], 0) ? -1.0 : +1.0); // 2400Hz
 	else
@@ -494,7 +501,7 @@ static MACHINE_CONFIG_START( alphatro, alphatro_state )
 	MCFG_DEVICE_ADD("usart", I8251, 0)
 	MCFG_I8251_TXD_HANDLER(WRITELINE(alphatro_state, txdata_callback))
 
-	MCFG_DEVICE_ADD("usart_clock", CLOCK, 19225)
+	MCFG_DEVICE_ADD("usart_clock", CLOCK, 19200)
 	MCFG_CLOCK_SIGNAL_HANDLER(WRITELINE(alphatro_state, write_usart_clock))
 
 	MCFG_CASSETTE_ADD("cassette", alphatro_cassette_interface)
diff --git a/src/mess/drivers/d6800.c b/src/mess/drivers/d6800.c
index c19bc2100e1..97fc58b5f8c 100644
--- a/src/mess/drivers/d6800.c
+++ b/src/mess/drivers/d6800.c
@@ -94,6 +94,7 @@ protected:
 private:
 	UINT8 m_rtc;
 	bool m_cb2;
+	bool m_cassold;
 	UINT8 m_cass_data[4];
 	UINT8 m_portb;
 	virtual void machine_start();
@@ -212,6 +213,12 @@ TIMER_DEVICE_CALLBACK_MEMBER(d6800_state::d6800_c)
 {
 	m_cass_data[3]++;
 
+	if (BIT(m_portb, 0) != m_cassold)
+	{
+		m_cass_data[3] = 0;
+		m_cassold = BIT(m_portb, 0);
+	}
+
 	if (BIT(m_portb, 0))
 		m_cass->output(BIT(m_cass_data[3], 0) ? -1.0 : +1.0); // 2400Hz
 	else
diff --git a/src/mess/drivers/dolphunk.c b/src/mess/drivers/dolphunk.c
index 11a1005d071..a829ac92feb 100644
--- a/src/mess/drivers/dolphunk.c
+++ b/src/mess/drivers/dolphunk.c
@@ -108,6 +108,7 @@ private:
 	UINT8 m_cass_data;
 	UINT8 m_last_key;
 	bool m_cass_state;
+	bool m_cassold;
 	bool m_speaker_state;
 	required_device<cpu_device> m_maincpu;
 	required_device<speaker_sound_device> m_speaker;
@@ -165,6 +166,12 @@ TIMER_DEVICE_CALLBACK_MEMBER(dauphin_state::dauphin_c)
 {
 	m_cass_data++;
 
+	if (m_cass_state != m_cassold)
+	{
+		m_cass_data = 0;
+		m_cassold = m_cass_state;
+	}
+
 	if (m_cass_state)
 		m_cass->output(BIT(m_cass_data, 1) ? -1.0 : +1.0); // 1000Hz
 	else
diff --git a/src/mess/drivers/fc100.c b/src/mess/drivers/fc100.c
index 7d32d59d60c..cd4b9683ea2 100644
--- a/src/mess/drivers/fc100.c
+++ b/src/mess/drivers/fc100.c
@@ -74,6 +74,7 @@ private:
 	UINT8 m_inv;
 	UINT8 m_cass_data[4];
 	bool m_cass_state;
+	bool m_cassold;
 	UINT8 m_kbd_count;
 
 	required_device<cpu_device> m_maincpu;
@@ -373,6 +374,12 @@ TIMER_DEVICE_CALLBACK_MEMBER( fc100_state::timer_c )
 {
 	m_cass_data[3]++;
 
+	if (m_cass_state != m_cassold)
+	{
+		m_cass_data[3] = 0;
+		m_cassold = m_cass_state;
+	}
+
 	if (m_cass_state)
 		m_cass->output(BIT(m_cass_data[3], 0) ? -1.0 : +1.0); // 2400Hz
 	else
diff --git a/src/mess/drivers/h8.c b/src/mess/drivers/h8.c
index ab75b43250b..8ae98ff76d8 100644
--- a/src/mess/drivers/h8.c
+++ b/src/mess/drivers/h8.c
@@ -84,6 +84,7 @@ private:
 	bool m_ff_b;
 	UINT8 m_cass_data[4];
 	bool m_cass_state;
+	bool m_cassold;
 	virtual void machine_reset();
 	required_device<cpu_device> m_maincpu;
 	required_device<i8251_device> m_uart;
@@ -278,6 +279,12 @@ TIMER_DEVICE_CALLBACK_MEMBER(h8_state::h8_c)
 {
 	m_cass_data[3]++;
 
+	if (m_cass_state != m_cassold)
+	{
+		m_cass_data[3] = 0;
+		m_cassold = m_cass_state;
+	}
+
 	if (m_cass_state)
 		m_cass->output(BIT(m_cass_data[3], 0) ? -1.0 : +1.0); // 2400Hz
 	else
diff --git a/src/mess/drivers/mekd2.c b/src/mess/drivers/mekd2.c
index b0edcda10fc..da01f1891cc 100644
--- a/src/mess/drivers/mekd2.c
+++ b/src/mess/drivers/mekd2.c
@@ -120,6 +120,7 @@ private:
 	UINT8 m_digit;
 	UINT8 m_keydata;
 	bool m_cass_state;
+	bool m_cassold;
 	required_device<cpu_device> m_maincpu;
 	required_device<pia6821_device> m_pia_s;
 	required_device<pia6821_device> m_pia_u;
@@ -329,6 +330,12 @@ TIMER_DEVICE_CALLBACK_MEMBER(mekd2_state::mekd2_c)
 {
 	m_cass_data[3]++;
 
+	if (m_cass_state != m_cassold)
+	{
+		m_cass_data[3] = 0;
+		m_cassold = m_cass_state;
+	}
+
 	if (m_cass_state)
 		m_cass->output(BIT(m_cass_data[3], 0) ? -1.0 : +1.0); // 2400Hz
 	else